Karim Sabri / ctools

…ract ctool::run() method (#3592)

…cripts now from csobservation instead of cslikelihood since they do not use proper optimizers.

The void constructors from ctools base classes are never used, tools are always constructed with a name and version number.

All likelihood ctools now derive from the ctlikelihood base class. This avoids code duplication and provides all likelihood tools with a uniform interface.