Added a new function get_aliases() which contains the declaration for a
static map which contains all aliases.
Changed the module_t constructor to register aliases
Removed leftover init_modules and init_aliases from cdo.cc
reworked register_operators into a function that registers a single
operator and used this function inside the module_t constructor
Added Alias struct which only purpose is to be created inside the
creation of a module_t. Helps to identify what is done and allows
creation of aliases in the same static manner as operators.
Fixed bandit tests.