adding a cmf_is_linkable twig function / templating helper
adjust test, we have added one funtion to the extension
Merge remote-tracking branch 'origin/master' into cmf_is_linkable

Conflicts:
	Templating/Helper/CmfHelper.php
some cleanup
Merge remote-tracking branch 'origin/master' into cmf_is_linkable

Conflicts:
	Templating/Helper/CmfHelper.php
update changelog, fix branch alias
Merge pull request #122 from symfony-cmf/cmf_is_linkable

adding a cmf_is_linkable twig function / templating helper