Tests: allow to limit execution time

By default the (stress-)test runs forever or until <Enter> key is hit.
Tests: add tests.xml

Note that it only reffers the (stress-/unit-)test, not the benchmark.
Improve debugging messages
Fix warnings about unused variables
[tests] Do not build custom daemon for stresstest
Tests: cleanup references to application code
Cleanup project files

Notes:

1. Ut_MRemoteThemeDaemon will not be imported from libmeegotouch as
   MRemoteThemeDaemon is not part of mthemedaemon API and is only used
   in test code - removing 'friend class' declaration.
2. IMAGESDIR was only used on single place while there are file paths
   hardcoded on many other places - removing now, maybe replacing
   globally in future.
Extract common qmake stuff into common.pri

Note: enabling QT_USE_FAST_OPERATOR_PLUS required minor adjustments to
QDir initialization.
Use temporary static lib to share code with tests
Move tests under tests/ directory

This also renames the 'mthemedaemontest' binary to 'stresstest'.
[tests] Import ut_mthemedaemonprotocol from libmeegotouch

Imported from revision fc20afc251f00bb7637da48c57eccb199a842367
ut_mthemedaemonprotocol: remove refs to libmeegotouch

Related commit:

15eeb3a Remove refs to libmeegotouch from imported code
ut_mthemedaemonprotocol: include in build again
[tests] Import ut_mcommonpixmaps from libmeegotouch

Imported from revision fc20afc251f00bb7637da48c57eccb199a842367
ut_mcommonpixmaps: remove refs to libmeegotouch

Related commit:

15eeb3a Remove refs to libmeegotouch from imported code
ut_mcommonpixmaps: include in build again
[tests] Import ut_mimagedirectory from libmeegotouch

Imported from revision fc20afc251f00bb7637da48c57eccb199a842367
ut_mimagedirectory: remove refs to libmeegotouch

Related commit:

15eeb3a Remove refs to libmeegotouch from imported code
ut_mimagedirectory: include in build again
Tests: always use exec wrapper

Prerequisite for next commit.