Update Docker base image Ubuntu Bionic 18.04

Stay up to date with latest Ubuntu LTS.
Also updates default target Python3 CrystaX version to 3.6.

Author: AndreMiras

Dockerfile

@@ -11,7 +11,7 @@
 # TODO:
 #	- delete archives to keep small the container small
 #	- setup caching (for apt, pip, ndk, sdk and p4a recipes downloads)
-FROM ubuntu:16.04
+FROM ubuntu:18.04
 
 
 # get the latest version from https://developer.android.com/ndk/downloads/index.html

pythonforandroid/recipes/python3crystax/__init__.py

@@ -12,7 +12,7 @@
 
 
 class Python3Recipe(TargetPythonRecipe):
-    version = '3.5'
+    version = '3.6'
     url = ''
     name = 'python3crystax'