Luigi Tibaldo / ctools

A specific parameter reloading is needed in case that command line parameters are provided.

This makes sure that the code also work in absence of the parameter file or a sysfiles folder.

Remove ctools::time_reference constant and handle the time reference for MET either by using the time reference from the input observation, or by adding a hidden "mjdref" parameter. The following tools transparently use the time reference of the input observation:
* ctselect (apply time reference of each input observation)
* ctbin (apply time reference of first input observation)
* csobsselect (apply time reference of each input observation)

A "mjdref" parameter was added the following tools:
* ctobssim
* cslightcrv
* cspull
* csviscube
* csobsdef

…meters were already queried

# Conflicts:
#	src/Makefile.am

The outcome of the unit tests depends on the presence of the CTOOLS environment variable. If the CTOOLS environment variable is not present the unit test should fail, otherwise it sould succeed.

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

The ctool::get_roi() replaces some duplicated code in ctselect and ctcubemask. The method extracts the RoI from the user parameters "ra", "dec" and "rad". In case the "usepnt" parameter is present and set to "yes", the "ra" and "dec" parameters will not be read, and it's up to the client to set the RoI centre properly.

The ctobservation::first_unbinned_observation() and ctobservation::next_unbinned_observation() methods implement an unbinned CTA observation iterator. Using this iterator avoids code duplication and generates a uniform interface for tools to loop over CTA events lists.

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