Big improvements for the custom elements system, some other changes.
* People can now use the content inside each custom element (<wcontent>)
* Add tagname attribute to <welement>, the custom element registration is changed
, now only one call is needed for a whole custom element file
* Can now perform initialization via the method Init of custom element model
to make custom behaviors for custom elements
* Recognize true/false in the bind string syntax
* Add len() helper
Merge branch 'master' of github.com:phaikawl/wade
forgot to reenable the uncommented for testing part in app.go

Conflicts:
	testapp/TodoMVC/app.go