Implementation of syntax highlighting

This commit introduces a new package (poc.highlight) that handles syntax highlighting for templates.

* Document partitioner
A change was necessary in order to have all the document parsed again on source update.

* Source viewer configuration
The new scanner had to be provided to the DefaultDamagerRepairer

* Highlight
Scanners, rules and tokens have been added
Fix error on partitioner when a new document is created

The region property was not correctly initialized in the constructor of the document partitioner.