Doc: make the Android setup instructions more prominent

Feedback from users indicates that they cannot find the
instructions for setting up the Android development environment.
Added links to the instructions in several high level topics.
Also, moved the Qt 5 instructions above the Qt 4 instructions
in "Connecting Android Devices".

Change-Id: Ie31bc27b959ac5a7146f00a576a900b932c07a98
Reviewed-by: Martin Smith <martin.smith@digia.com>
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Reviewed-by: Nico Vertriest <nico.vertriest@digia.com>