Use a more universal shebang

On FreeBSD, php is usually in /usr/local and I'm sure there are many more exceptions.
delete old previews
Add notes that SQLite is CE only
Markup corrections
added comment that App Store is disabled for EE
Correctly namespace DatabaseSetupException
Don't show favicon to prevent iteration through subfolders

The codepath for generating the favicons iterates through subnodes and if one of those nodes is unavailable is throwing a 503 exception. Since these favicons don't have any use except of "making a tool for developers looking nicer" I consider it feasible to remove them.
Move constants from GET_TYPE to OC\Files so they can be autoloaded
remove deprecated \OC:$session
Merge pull request #12453 from owncloud/kill-session-global

remove deprecated \OC:$session
Merge pull request #12448 from owncloud/no503forRoot

Don't show favicon to prevent iteration through subfolders
Merge pull request #12304 from oparoz/patch-1

Use a more universal shebang
Merge pull request #12433 from owncloud/appstore

added comment that App Store is disabled for EE
Cache results of available languages

This function is about 8 times calles for every single page call, when caching this variable I was able to gain a small performance improvement from 20,512 µs to 630 µs profiled with xhprof

Surely, this is no gigantic gain but if we would do that for every function out there...
[tx-robot] updated from transifex
Merge pull request #12451 from owncloud/issue/6101-remove-gettype-class

Move constants from GET_TYPE to OC\Files so they can be autoloaded
Correctly namespace and autoload DatabaseException
Replace exception with standard exception
Merge pull request #12464 from owncloud/cache-available-languages

Cache results of available languages
Introduce getSourcePath() in Storage\Local to reduce the difference to MappedLocal