tests: Build tests into separate executables

Allow selectively run single test cases and produce useful reports on
the pass/fail ratio.
tests: Add make check target
tests: ServerSessionHandlerTest: set DB file path

Broken since ec17dfc (moving to development on meego.gitorious.org) when
the default path moved from /tmp/... to /etc/... (permission denied).
tests: SessionHandlerTest: fix cleanup routine

Broken since 70864c5 ([buteo-syncml] Fix profile removal - set absolute
file path when calling setDatabaseFilePath())
tests: SyncAgentTest: Fix library reference for Qt5
NonceStorage: Fix typo in SQL query

[buteo-syncml] NonceStorage: Fix typo in SQL query