Use isset() instead of strlen()

Cache results of `normalizePath`

Add CSRF check to search

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

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replace outdated 'shared' people icon with regular share icon as fallback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

Otherwise when the file without any specified mimetype was accessed the error log was flooded with entries such as "Undefined index: mime", there can be multiple issues found about this in the forum and our bugtracker.

To test this access `/index.php/apps/files/ajax/mimeicon.php` with and without `$_GET['mime']`.

Fixes itself.

Verify whether type is correct

Logfile download

`$this->info` can very well contain an empty array or possibly other values. This means that when this code path is called a PHP Fatal error might get thrown which is not what we want.