This refactors the filter guide docs into a single file.
Also removes out of date references to the fact that Angular used to enhance Arrays while evaluating expressions.

We have links to better videos now on the guide/index page.  This one's time has past.

Before, there we multiple overview docs:
- guide/overview
- guide/introduction
- guide/dev_guide.mvc
- guide/dev_guide.mvc.understanding_model
- guide/dev_guide.mvc.understanding_view
- guide/concepts

Now we have:
- guide/introduction: High level description of Angular with the key benefits but without code or any concrete concepts
- guide/concepts: explains all important concepts with a simple example and contains deep links to the other parts of the guide.

 All the old information was moved into existing documents or deleted when they were duplicates.

The example about transclusion and scopes worked only because the order of `scope` and `element`
arguments is wrong, which means that the `name' property of the scope is not really being updated.
To really work, the directive has to define its own scope, either a new child scope or, as is more
common with transclusion, an isolated scope.

Closes #4774

Closes #4748

Broken - $scope.spicy = 'very';
Works - $scope.spice = 'very';

Closes #4752

Inserted a couple of line breaks to increase readability.

Closes #4756