[REFACTOR] removed StopWatch class

Always make sure that you wrap an existing API at least one time.
Although this almost never gains you any benefit you can argue that you
enhanced the API with *no value* and only pollute the code base and at
least produced some LOCs.

Sorry for this commit message but this hurts my eyes and gives me a
headache.

Change-Id: Id754b1f53e26ad2ba9660dcc999dd3face7eef7b
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1144
Tested-by: Jenkins CI
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>