feat: add option to use external css rewriter in template_cache_generator.

The provided rewriter will be used to transform every css read by the
TemplateCache, the original css is provided on stdin, and result is read
from the stdout of provided binary.

TESTING:

The test uses a simple sed script to exercise the integration.

The test runs only if sed is present on the running system.  The test
uses CSS with simple rules that are being translated for RTL locales.

Closes #1052
feat(NodeAttrs): Node attributes don't get initialized by NodeAttrs when
setting up observing.

In case an element does not have a value set for a propertyv, that
property is not automatically initialised. For example:

  <div test foo="bar">

will cause ElementBinder to register observer (which will in turn cause
initialisation) on property foo (of the directive) to bar, but if we try
using

  <div test>

foo property will not be initialised.

Closes #1001
feature(directive_injector): add View to DirectiveInjector

Some directives require access to the current view. Add the view field to the DirectiveInjector class, so it can be injected.

Closes #1293