Handling long paths properly in \OC\Files\View

We now support a maximum path of 4000 characters.

Php is limiting us to 4096 (260 chars on Windows :dancers:).
Due to maximum column length on Oracle for a varchar columns being 4000 - this is our new max path length. (I don't want to summon this migration horror on us)

@karlitschek @craigpg @icewind1991 @PVince81 @schiesbn 

This is no the end of the road - more to come .....

further tasks https://github.com/owncloud/core/issues/8571