Allow expression tags in main content templates.
migrate calc example to 2.2-parser
filters has to be include before validators
Merge pull request #2 from dingsda87/migrate/parser

migrate calc example to 2.2-parser
ID#220 remove reference operator (&) when assigning objects
since PHP 5 copying objects means that only their internal pointer is copied
to the new variable (unless clone is used). so there is no nead to use & for that.