[tests] Allow to execute tests on target

Originally it was supposed tests would be executed inside build dir.

Notice that env.py.in and env.sh.in have not been left unused after f79e5b1 - removing now.

Relates NEMO#520
[libcontentaction] mlite no more using mlocale

mlite library no more rely on mlocale library to localize desktop entry
name and no alternative mechanism to implement the functionality behind
CONTENTACTION_L10N_PATH environment variable is provided by mlite at the
moment -- removing the feature.  To make 'lca-tool --l10n' tests pass
without the possibility to use CONTENTACTION_L10N_PATH, absolute paths
are specified for the X-MeeGo-Translation-Catalog key.

Relates NEMO#520
[tests] Compile '-idbased' translation catalogs

mlite uses qtTrId() to localize desktop entry name.

Relates NEMO#520