Add support for selecting account when sharing from outside apps (#1011)

* Add direct-share support (API 23+)

* Add account selection dialog for non-direct sharing

app/src/main/java/com/keylesspalace/tusky/interfaces/AccountSelectionListener.kt

@@ -0,0 +1,22 @@
+/* Copyright 2019 Levi Bard
+ *
+ * This file is a part of Tusky.
+ *
+ * This program is free software; you can redistribute it and/or modify it under the terms of the
+ * GNU General Public License as published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * Tusky 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 General
+ * Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with Tusky; if not,
+ * see <http://www.gnu.org/licenses>. */
+
+package com.keylesspalace.tusky.interfaces
+
+import com.keylesspalace.tusky.db.AccountEntity
+
+interface AccountSelectionListener {
+    fun onAccountSelected(account: AccountEntity)
+}