GPII-345: Adding a new and functional GPII Activity

This commit brings a new UI for the Android's GPII application activity.
Within the new design, we're providing some useful features to the user.

  * start/stop/kill the GPII instance of the device through the UI
  * Check the current status of GPII

Do do that, we've made the following changes:

  * Create the layout for the new UI
  * Include the Java code for the new UI
  * Add all the translatable stings into strings.xml
  * Add the logo of the GPII project
Merge remote-tracking branch 'javihernandez/GPII-345'
GPII-345 Minor indent change.