Merged all licensing info into a single file to avoid APK build problems.

LICENSE.txt

@@ -13,6 +13,23 @@
     You should have received a copy of the GNU General Public License
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
+-------------------------------------------------------------------------
+
+    All files under the directories briar-android/src, briar-api/src,
+    briar-core/src, briar-desktop/src and briar-test/src are licensed
+    under the Apache License, version 2.0 (the "License"); you may not
+    use these files except in compliance with the License.
+
+    You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+    implied. See the License for the specific language governing
+    permissions and limitations under the License.
+
 -------------------------------------------------------------------------
 
                     GNU GENERAL PUBLIC LICENSE