[#ENYO-1712] refactor PhoneGap build to enable signing keys

This is the first of 2 PR's to cope with new PhoneGap Build security change introduced on December 12th:  https://build.phonegap.com/blog/upcoming-security-changes

* ENYO-1712: Add a link to manage PhoneGap build signing keys. (HEAD, enyojs/ENYO-1712, ENYO-1712)
* Merge branch 'master' of github.com:enyojs/ares-project into ENYO-1712
* ENYO-1712: check PhoneGap credentials & retrieve account details
* ENYO-1712: add an explicit `authorisation` step to PhonegapBuild (micro-tech/ENYO-1712)
* ENYO-1712: catch `onUpdateAuth` events at `Ares()` level (top-most)
* ENYO-1712: ServiceRegistry: Add generic `<Service>#authorize()`
* ENYO-1712: LocalStorage: bind callbacks only when `self` is provided
* ENYO-1712: remove nodejs-file-server.js archived by default
* ENYO-1712: remove direct bdPhoneGap dependency on node-formidable
* Revert "ENYO-1223: add node-formidable multipart/form-data upload manager"
* ENYO-1712: add dependency on node-mime (MIT-licensed)
* ENYO-1712: add dependency on `https://github.com/mikeal/request` (whatfield73/ENYO-1712)
* ENYO-1712: make ares filesystem-layout more bootplate-like (2)
* ENYO-1712: remove unused mapped folders
* ENYO-1712: remove phonegapbuildapi & re-add as a git submodule
* ENYO-1712: make ares filesystem-layout more bootplate-like

Enyo-DCO-1.1-Signed-off-by: Francois-Xavier KOWALSKI <francois-xavier.kowalski@hp.com>