New XML tag syntax to invoke templates

Supports `<tone:header title="MyTitle" />` as an alias to `<% use(header.class).render("MyTitle"); %>`.

Very simple implementation, regex-based. Only supports String parameters, with everything optional, and one code block (tag body).

/cc @guilhermesilveira @mauricioaniche 
i.e.: String SELF_CLOSING_TAG = "/>$"
OPEN_TAG = ">$"
then you can remove the comments