Cleaning up the Directive implementation.

https://github.com/kyoken74/gwt-angular/issues/36
Working on directives.

It's getting there... The inclusion of text as template works. The 
inclusion of data resource (i.e. partial) via templateUrl works. The
restrict seems to be working though not tested, etc, but the one I care
about right now most, the value of the directive attribute, is somehow
not working yet.

https://github.com/kyoken74/gwt-angular/issues/36
Moved the sample directive to tutorial section for convenience.

Getting closer to have this working. Doesn't seem to when the directive
is inherited from an external module. We get $digest already in progress
error.

https://github.com/kyoken74/gwt-angular/issues/36