[buteo-syncfw] Introduce DEFINES+=USE_KEEPALIVE

Introduce platform specific code that uses the nemo-keepalive apis.
All existent code is kept intact when this new DEFINES is not used.
This commit also reverts some of changes done by 7674c260812b8656f18e40e58f92efd2e7f8228e
Merge pull request #33 from nemomobile/global-timers

[buteo-syncfw] Introduce DEFINES+=USE_KEEPALIVE
[buteo-syncfw] Emit network error if session is not open in less than 10secs

In some conditions Qt network layer can take some time to fail,
since msyncd runs as a background process is not desirable to wait
long for a network request reply, with this PR if no reply comes in 10secs
a network error is emitted.
Merge pull request #34 from nemomobile/keepalive

[buteo-syncfw] Emit network error if session is not open in less than 10secs
[buteo-syncfw] Correctly depend on the library, don't just pray it builds in time.
[debug] Support msyncd -d for debug logs

This replaces the no-longer-available /etc/buteo/set_sync_log_level method
[debug] Support debug messages in debug builds