RemPos v2.1

Replace selfmade json library with nlohmann json.
Downgrade compatibility to C++17
rempos::senzor_server and rempos::RemPos are no longer movable and copyable
Make rempos::RemPos members to be inside the class. (Were pointers before)
Proper variable naming in gmsv_rempos.
Wrap rempos_server to unique_ptr.
Change asserts to separate branch with error.

RemPos 2.0

Rebuilding from scratch for new app and new library.