This creates a docker container for building QGIS for android

Usage:
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For setting up a developer environement from the current directory run
  docker build .

For setting up a build server do 
  mv Dockerfile Dockerfile-developer
  mv Dockerfile-buildserver Dockerfile
  docker build .


Development:
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The Qt SDK installer is a piece of software that only works with a GUI dialog
and that is not what we want it to do here. So we had to do some work in order
to get the SDK into the docker image. now all should build automatically. 
but if you want to reproduce the steps, here they are:

 * Download the latest Qt SDK. Host arch: 64 bit, Target arch: 32 bit
 * Install it locally
   * to /usr/src/qt
   * cd /usr/src/qt
   * tar -zcvf qt5.3.1.tar.bz2 Qt5.3.1
   * mv qt5.3.1.tar.bz2 THIS-FOLDER/files