Don't double encode string

Simplify isValidPath and add unit tests

Verify whether value is already normalized

Use isset() instead of strlen()

Cache results of `normalizePath`

Add CSRF check to search

Apparently `normalizer_normalize` is not verifying itself whether the string needs to be converted or not. Or does it at least not very performantly.

This simple change leads to a 4% performance gain on the processing of normalizeUnicode. Since this method is called quite often (i.e. for every file path) this has actually a measurable impact. For examples searches are now 200ms faster on my machine. Still not perfect but way to go.

Part of https://github.com/owncloud/core/issues/13221

Isset is a native language construct and thus A LOT faster than using strlen()

On my local machine this leads to a 1s performance gain for about 1 million paths. Considering that this function will be called a lot for every file operation this makes a noticable difference.

`normalizePath` is a rather expensive operation and called multiple times for a single path for every file related operation.

In my development installation with about 9GB of data and 60k files this leads to a performance boost of 24% - in seconds that are 1.86s (!) - for simple searches. With more files the impact will be even more noticeable. Obviously this affects every operation that has in any regard something to do with using OC\Files\Filesystem.

Part of https://github.com/owncloud/core/issues/13221

Cache responses from the AppStore server

We already use `.text()` here which automatically properly encodes the string. Thus the string will be double-encoded and look ugly. (i.e. when you search for ">" you will see "No results found for >")

Fixes itself.

The check for invalid paths is actually over-complicated and performed twice resulting in a performance penalty. Additionally, I decided to add unit-tests to that function.

Part of https://github.com/owncloud/core/issues/13221

Doesn't hurt to have a check on this one as well.

Otherwise every time the AppStore was opened a lot of connections to the AppStore server were made which resulted in a terrible performance.

This changeset will cache the response for a sensible time so that only the first request will be somewhat slow.

Performance changes:
- Loading a category took previously more than 3 seconds on my machine. Now for every follow-up request it takes less than 200ms, resulting in a performance gain of 1950%
- Loading the category list took previously about 750ms - now it takes 154ms, a total performance gain of 395%

Encryption fix key lost if group share gets renamed

Fix reshare permission issue

HHVM Workaround: Do not use Exception from Stream.

Use memcache for findBinaryPath

Works around https://github.com/facebook/hhvm/issues/2436#issuecomment-69351373

Add check if user is logged-in

Fix js error in personal settings if there is no password field

replace outdated 'shared' people icon with regular share icon as fallback

The actual share permissions sent to the server on reshare are now based
on possiblePermissions + permissions inherited from parent share

Trim leading or trailing slashes in file cache paths

Default to reusing etags in the scanner

It's slow, this makes it fast!

Use Doctrines filter by table name

fix rename field position, fix #12927

Otherwise a fatal PHP error is thrown since the filesystem is not setup:
```
( ! ) Fatal error: Call to a member function getOwner() on null in /Users/lreschke/Programming/core/lib/private/files/filesystem.php on line 817
Call Stack
1	0.0004	247792	{main}( )	../index.php:0
2	0.0946	5088776	OC::handleRequest( )	../index.php:28
3	0.1423	7491280	OC\Route\Router->match( )	../base.php:748
4	0.1664	8592152	call_user_func:{/Users/lreschke/Programming/core/lib/private/route/router.php:250} ( )	../router.php:250
5	0.1664	8592216	__lambda_func( )	../router.php:250
6	0.1665	8599064	require_once( '/Users/lreschke/Programming/core/apps/files_versions/ajax/getVersions.php' )	../route.php(135) : runtime-created function:1
7	0.1801	9061096	OCA\Files_Versions\Storage::getUidAndFilename( )	../getVersions.php:7
8	0.1801	9061144	OC\Files\Filesystem::getOwner( )	../storage.php:45
```

Furthermore this adds the CSRF check as a nice-to-have addition, the requests accessing this are done via the jQuery AJAX methods and thus the header is automatically added to all requests already.

Ldap user cleanup master

Verify existence of $_GET key