Add root/current view model awareness to PhpRenderer
Add root/current view model awareness to PhpRenderer

- New view helper, ViewModel, for composing the root and current view model
- Added getRenderer() method to PhpRendererStrategy
- Modified Bootstrap to inject ViewModel helper with base view model instance
- Use cases:
  - Changing layout template
  - Injecting layout with variables from child views

svycka/zend-mvc,ezimuel/zend-mvc,MadCat34/zend-mvc,turrsis/zend-mvc,turrsis/zend-mvc,svycka/zend-mvc,ezimuel/zend-mvc,MadCat34/zend-mvc