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

# Cagou: desktop/mobile frontend for Salut à Toi XMPP client
# Copyright (C) 2016-2019 Jérôme Poisson (goffi@goffi.org)

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Affero General Public License for more details.

# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.