ENYO-2949: better specify `overwrite: undefined/true/false`

- `overwrite != false` means `overwrite = true`
- add file-system test cases
- set file-manager operations create/copy/move to `overwrite=false`

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
Merge branch 'ENYO-2949' of github.com:enyojs/ares-project into ENYO-2949
ENYO-2949: add overwrite option to `MKCOL` & update `createFolder|File`

- MKCOL  Hermes verb  now support  the `overwrite`  optional parameter
  (default: true)
- Document protocol change in `hermes/README.md`
- Enrich test suite to ensure non-regression in 
  `test/server/fs.spec.js`
- `HermesFileTree#createFolder` &  `HermesFileTree#createFile` now use
  `overwrite=false` by default.

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
Merge branch 'master' of github.com:enyojs/ares-project into ENYO-2949

Conflicts:
	hermes/README.md
ENYO-2949: code review comment: add missing options parameter

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
ENYO-2949: start using generic XHR error handler & global Ares error popup

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>
Merge pull request #513 from enyojs/ENYO-2949

merged