FIX: copy gaia/profile-debug/user.js to addon/template/profile (fix NotSupportedError on desktop-helper touch-events.js)

Gaia user preferences generated by "gaia/build/preferences.js"
are now located on "gaia/profile-debug/user.js" and needs to be
copied over "addon/template/profile/user.js" to activate
custom desktop-helper preferences.

"dom.w3c_touch_events.enabled=1" user_pref fix the exception and
touch-events.js emulation helper from desktop-helper works again
(e.g. the FirefoxOS statusbar can be dragged again).
Merge pull request #852 from rpl/fix/touchevents-not-supported-error

Bug 926540 - copy gaia/profile-debug/user.js to addon/template/profile r=@ochameau