[FEATURE] Iterator / Filter ViewHelper

Selects values or objects with properties matching a given filter.
[FEATURE] ViewHelperUtility for reusable methods
[TASK] Test cleanups and improvements
[TASK] Fix CGL issue in Iterator / Filter ViewHelper
[FEATURE] Add raw array/iterator key support to Var / Get ViewHelper

Fixes: #362
Merge pull request #385 from NamelessCoder/filtervh

[FEATURE] Iterator / Filter ViewHelper
Merge pull request #386 from NamelessCoder/getrawkeys

[FEATURE] Add raw array/iterator key support to Var / Get ViewHelper
[BUGFIX] Correctly treat overwrite setting of assets
Merge pull request #387 from tantegerda1/master

[BUGFIX] Correctly treat overwrite setting of assets