Buf3D lego instructions support

[Antonio Cortés Carrillo]

Hello Steffen, Jason and Ignacio. The new version fixes some problems (not all):

* Support for standard ActionBar (compatible version with the old android 2.1)
* Back Button no longer running last app.
* Wrong words in english
* Back button no longer accesses to model load

In addition:
* Full screen in android 4.4

Pending:
* Some bugs to cancel loading
* Background color (more accessible)
* Background image
* Preference screen incorrect display