Bower: Ignore development and documentation files on bower.json. Fix #10313.

I've kept only the files I consider relevant to bower installation:

- Files in dist directory;
- Files in js directory;
- Files in less directory;
- bower.json file;
- README.md file;
- LICENSE file.
bower.json: Modify `assets` directory on ignore to `docs-assets`
Merge pull request #10353 from rwillrich/ignore-files

Bower: Ignore development and documentation files on bower.json. Fix #10313