Split `app/templates` into its own tree.

Currently, we are processing the entire `app/templates` and `app/styles`
directories for all `preprocessJs` filters (this means things like
`ES3SafeFilter` are actually checking each template).

This makes `templates` it's own tree, and splits things up
appropriately.
Fix tree returned by addonTreesFor('styles') not being included
Merge pull request #1238 from rjackson/split-templates-tree

Split `app/templates` into its own tree.
Merge pull request #1229 from aexmachina/styles-addon-trees

Tree returned by addonTreesFor('styles') is not included
Update blueprint blueprint
Merge pull request #1243 from jgwhite/blueprint-blueprint-update

Update blueprint blueprint
Do not watch nested directories again.

Without this change, two change events are triggered when a template or
style file is changed.
Merge pull request #1247 from rjackson/dont-double-watch-dirs

Do not watch nested directories again.