core, android: new share widget + added Cagou to "share" menu: - new intent filter to add Cagou to share menu for all media types - minimum Kivy version is now 1.11.0 - new "Share" widget to display data to share via SàT and select the target - new core.platform_ module (the suffix "_" avoid trouble with standard "platform" module), for platform specific code. - Android intent are now checked on startup and "on_new_intent" events - if a android.intent.action.SEND action is received (i.e. some data is shared), the "Share" widget is shown - new Cagou.share method to share data using "Share" widget - new Cagou.getAncestorWidget method to easily retrieve an instance of a specific class in a widget's ancestors - ContactList's Avatar and ContactItem widgets have been moved to core.common