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 
extract the pattern into a static constant, the name says what it does