Feature/enforce dynamic memory allocmodel

OK, this is the current state regarding #19 (closed).

TODOs:

• remove all traces of DYNAMIC_MEMORY_ALLOCMODEL
• remove manual heap management
• remove TOP/BOTTOM semantics of memory management
• unify different memory allocation methods
• remove user data from MG
• remove virtual heap management
• cleanup memory management in DDD
• make valgrind happy 😉

Three large topics are sorted out. the first part is only a some search/replace work, which will be done soon and then the important part of removing now obsolete data structures and functions will be the important part...

This MR is WIP. I still want to cleanup several commits and split this into a few separate MRs, but I wanted to get the discussion with @oliver.sander going.