Build: Specific copy:* and task descriptions

- Task descriptions are shown running `grunt --help`
- Adds new "assets" task for other files copied to the dist
- Move test/jshint call to the high level dist/debug chains
Bower: Don't exclude dot files

Some of these are required for the theme re-builds
Merge pull request #3173 from nschonni/v4-build-cleanup

Build: Specific copy:* and task descriptions