* set the creation of a graph off by default
* Major redesign in terms of the LSQ6 class. Now there is a base class in order to avoid to many duplications of code. Also, many of the LSQ6 classes deal with similar things, e.g., checking the initial model, resampling the input files and creating an average. The main part where they differ is in how they establish the transformation between the target and the source.
* added the option to use the -identity flag for minctracc when running an lsq6 registration
* Changed the option parser a bit, to be able to write a verbatim epilog at the end of the program help.
* Looks like (nearly?) finished LSQ6 module. Added the posibility to specify an lsq6 protocol for minctracc. By default, factors are used.
* added documentation to the LSQ6 module and changed the default settings for the lsq6 hierarchical minctracc class in case a simple/identity registration is performed.
Merge branch 'develop-lsq6'