So the class files only have class code and don't execute code

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...

because OC_User::login will create a new session we shall only try to login if user and pass are set

ensure to never destroy an existing session

Some PHPDocs were incorrect, also used this opportunity to replace some deprecated functions.

This is unused legacy code. Let it die with ~~~honor~~ fire.

Fixes https://github.com/owncloud/core/issues/12346

fix calculation of expiration date if there is a default expiration date set (but not forced) and the user does not want the link to expire.

This reverts commit 09fd34ee.

This is not installed by default in all cases and will break the DAV features of ownCloud. Lot's of reports such as https://github.com/owncloud/ios-issues/issues/167#issuecomment-63798507