don't render templates if the template tag is blank

[PetrDlouhy]

Partial fix for #158

The rendering of templates take ~10ms per scribble even if it's content is completely blank. This returns simply blank DIV in that case. Other changes are just rearranging order of commands, that shouldn't have influence on data processing.

This introduces small incompatibility - if the template was overriden by user, the blank output could differ. I would probable rewrite this, so that it would generate blank content once at startup.