feat(urls): support relative CSS / template URLs in components

Example:
When defining a component called 'foo' in file
'/myproject/has/many/folders/foo.dart', prior to the change you would
do so thusly:
@Component(
   selector: 'foo',
   templateUrl: '/myproject/has/many/folders/foo.html',
   cssUrl: '/myproject/has/many/folders/foo.css'
)

The above is still valid, but now can also be defined rather more
succinctly as:
@Component(
   selector: 'foo',
   templateUrl: 'foo.html',
   cssUrl: 'foo.css'
)

A full table of what URLs will be changed/unchanged is below:
You Say:				Transformer replies:
'packages/foo/bar.html'			'packages/foo/bar.html'
'foo.html'				'packages/foo/bar.html'
'./foo.html'				'packages/foo/bar.html'
'/foo.html'				'/foo.html'
'http://google.com/foo.html'		'http://google.com/foo.html'

*Note  that as  shown any absolute paths you define will not be
bothered by the transformer, so if you have a templateUrl living at
<root>/foo.html, you can still reach it with '/foo.html'!

This feature is defaulted to an "off" state through the addition
of the ResourceResolverConfig class.  We do this for backwards compatibility
in case users are already using relative urls from the root, i.e.:

'foo.html' should really reference '<root>/foo.html'.

Or other strange url definitions.  Eventually the backwards compatibility
feature will be defaulted to an "on" state.

To turn the feature on, bind
a new ResourceResolverConfig in your module:

module.bind(ResourceResolverConfig, toValue:
	new ResourceResolverConfig(useRelativeUrls: true));

*Testing*:
- e2e transformer tests can now be done on the sample application found
  in the test_transformers folder