add twig as possible template engine for rendering components

this is useful for:
- template inheritance
- autoescaping
- better syntax
convert from templates to twig

this allows dynamic form extend form without having to copy the whole template
allow components to override used template by returning 'template' in getTemplateVars

with that we don't need a template that manually includes.
This is needed for proper twig support
convert menu templates to twig
Merge pull request #252 from nsams/twig

add twig as possible template engine for rendering components