fixed help being copied, improved readability

* Help Changes
** now using CdoHelp type
** adapted code to use string_views from help

* Readability
** added struct FactoryEntry to improve readability
*** adapted code to the new FactoryEntry
*** FactoryEntry now used in std::map<std::string, FactoryEntry> for registering operators
** added typedefs in cdo_module for readability"

* Process
** removed default constructor from Process
** added Parameter CdoModule to Process constructor

* Factory
** Registration does no longer set Process values manually
** Process constructor is now used properly
** extracted std::function creation into a function (readability)

* Misc
** adapted tests
** removed some unrequired includes