Expanded one line if statement - Trivial

Oneliners are ugly.

Check if user is admin - bool

Let's remove it, it's also not secure anymore with the introduction of
our API etc...
(And doesn't work with ldap etc…)

Simplify the isSubDirectory() function

user_webdavauth - l10n - Trivial

allow default click behaviour

Thanks Jenkins!

There was no "isAdminUser()" function which returned bool. This is
irritiating as there were a loooooooot of places in the code which
checked this itself with `OC_Group::inGroup($uid, 'admin)` - why not
use a function for this?
(Especially if you consider that we might change the group name in the
future, which would lead to problems then)

Additionally, @Raydiation needed such a method for his AppFramework :)

otherwise /foo/bar would be detected as a subfolder of /bar

THX @icewind1991

This fixes a problem that prevented app routes from being loaded after ocs_api merge

This reverts commit 9d41322c.

Remove ugly indentation - Trivial

Conflicts:
	apps/files_versions/templates/settings-personal.php

isSubDirectory() checks if a specified $sub is a subdirectory of the
$parent, this is needed to prevent file inclusions.

Actually, the current code is more kind of a "hack" which I always
struggle over if browsing through source. So this should be a much
better implementation.

The implementation is really straightforward:
- [realpath()](http://php.net/manual/function.realpath.php) expands all
symbolic links and resolves references to '/./', '/../' and extra '/'
characters in the input path and return the canonicalized absolute
pathname.
- [strpos()](php.net/manual/function.strpos.php) returns FALSE if the
substring wasn't found.

Since this is an absolutely critical piece of code, I'd like to ensure
that this is absolutely safe!

Sounds better for me.

Update CONTRIBUTING.md

Thanks @eMerzh, could be especially needed as there are some platform specific issues like filename encoding under MS Windows

:oops:

Makes it at least better readable for me.

Move openid.php to apps repo

Conflicts:
	settings/routes.php