Custom File Explorer dialog has been dropped, we will delegate this action to
third party app, or to the Storage Application Framework (new in API 19).

Available on API 17 +

libccrtp was depending on commoncpp2, and have been replaced by a version
depending on ucommon as well.

Looks like a major update, with better performances for ARM.

Apk generated cannot be used on real devices, no need for now, but it could be useful
to have two types of builds: for tests on x86 emulator, and nightlies.

Rev 4716 introduces errors when building for android (miltiple definitions)

This commit reactivate unit testing in SFLphone android.
Tests are trivial for now, but will contribute in setting up the whole
testing process with jenkins.

The main issue here is due to the build system of the stack compared to a pure Android
NDK project. Generating arm and x86 ABI at the same time does not seem to be possible.

There is an issue in a UI element (ViewPager), which does not get properly populated
when restoring its state. (found using VMs with API=16)