Show warning when invalid user was passed

Warn for password reset when files_encryption is enabled

Only show undelete capability if files_trashbin is enabled

Fixes the OCS capability API at /ocs/v1.php/cloud/capabilities

User management search just searches users - adjust label of input field...

drop unneeded var_dump - fixes #9997

Replace deprecated switches

Use full path instead of only the filename

make sure that we don't find the wrong shares if a user and a group have the same ID

$file only contains the filename and not the absolute path, that means that files in a subdirectory will not get properly resolved and an empty filesize is returned.

This feature only exists on master.

Warning: -convert-to is deprecated.  Use --convert-to instead.
Warning: -outdir is deprecated.  Use --outdir instead.

Fix type hinting for app manager

Check if the size field is available

make sure that we only find the shares from the correct share type if users and groups with the same ID exists

Remove unused code

Make declaration compatible

Add tests for normalizePath() with absolute paths on windows

Fix remote.php routes for apps that are enabled for specific groups

In some cases the 'size' field is not available resulting in some PHP errors such as:

```json
{"reqId":"03548fd9e3d3aca15a5796b3b35d7b9d","remoteAddr":"::1","app":"PHP","message":"Undefined index: size at \/Users\/lreschke\/Programming\/core\/lib\/private\/files\/fileinfo.php#125","level":3,"time":"2014-11-17T21:38:57+00:00"}
```

This can be experienced when creating a new empty file and deleting it right away, then when going to the trash bin this error is thrown.

Move CSRF check

Fixes #12236

Creating a new key pair can take 1-2 seconds. So it could happen that the user click the "Reset password" button again which can lead to many nasty things, e.g. we could create two new key pairs in parallel.

THX @schiesbn
(I should setup a mail server on my local system...)