android: handle runtime permissions: - some mandatory permissions are requested on Cagou start, Cagou won't start at all and display a warning message if they are not granted (we request 5 times before showing the warning) - transfer plugin can now use "android_permissions" in plugin_info, to indicate what is necessary. The permissions will then be requested, and the plugin widget won't be shown if they are not granted (and a warning not will then be displayed)

f95d0c31d45558c7b3e2fc39398f51eb0190bdca 0.7.0a1
4233be74572a1af8eebd502c009a10641c63ca0c 0.7.0a3
5c28cf8815319abd8c963022091cf4726764a3e6 0.7.0b1
51f73d210da908c9fb292e6bd7fda42a9d2b8453 0.7.0