Deprecate older API wrappers and calls

Those old classes have now non-static pendants and can be deprecated IMHO.
add postfix

add postfix
Remove exec() call with invalid name on windows

Currently running unit tests prints the following message 3 times:
The command "command" is misspelt or could not be found.
Instead of trying this, we just skip this now.
Deduplicate function by moving it to the OC_Helper
Simplify the binary finding code in the movie preview class
Clean up the test data in tearDownAfterClass()

The result of the listener should then be empty and can be removed
Remove testcleanuplistener.php
drop OC_Preferences::getUsers and getApps
detect user display name attribute and return user count depending on its presence
consolidate user count filter in wizard and user back end
detectors (email, displayname..) are now started in one place, triggered from only 2 places. more reliable structure and flow, saves requests
to reassure that selected attributes still work, do not count all matching entries but limit it to 1 in order to make it faster
a corrected email attribute needs to be saved, not only returned
JS doc
this happens already before counting, no need anymore
use underscore.js for undefined checks
better readbility, no effective changes
phpdoc and mixed up letters
trigger count on the correct filter
Merge pull request #12336 from owncloud/drop-getApps-getUsers

drop OC_Preferences::getUsers and getApps