Add more scope attributes.

Attributes added to block logical operator keywords and to punctuation
keywords such as assignment "=".
Fix filter syntax parsing

Filter syntax checking was far too greedy and complex before, leading
to unexpected behavior when multiple values were given in the same tag,
etc.
Change certain keyword scopes

Scopes for: reversed, only, with, by, as
Changed from: keyword.operator.other
Changed to: keyword.other
Add dynamic scope names to tags

Tags such as {% block content %} will now receive a scope attribute
"meta.scope.django.template.tag.block.content".  This spans the entire
body of the tag's contents, and also includes the open/close tags
themselves.