[BUGFIX] Add input string argument to Format.Crop ViewHelper

The Format.Crop ViewHelper did not provide a way to pass
the input string as simple argument; this patch now allows
this. An appropriate UnitTest is added; additionally an
augmentation to the ViewHelpers' DocComment, mentioning an
inline use case, is added.

Change-Id: Ia744fb10bf2e85c529c7c0b2629a8fa9c362e5a8
Releases: master
Merge "[BUGFIX] Add input string argument to Format.Crop ViewHelper"