Added HotState.
Added HotStateSet.
Added HotTransition.
Added an incomplete implementation of a CARTA.
Implemented a simple CARTA.
Changed order in Makefile.

Otherwise a linker error happens when library is used.
Basic string_of implementation for CARTA.
CARTA now creates their own ranked alphabet, term and states module.
Simplified CARTA. It only needs a ranked alphabet for instantiation.
Distinguished path = epsilon for string_of_state.
Type of Term.re was abstract in CARTA and SimpleCARTA.
Removed types from string_of state's path.
Added drain state.