Added array heap management; vector? and make-vector

1) Added `vector?` and `make-vector` native functions;
2) Greatly refactored memory management; CELL_ARRAY;
2a) Added private CELL_FREE, CELL_ARRMETA cell types;
3) Renamed print_list/printc functions info dbg_print*
4) Added some predefined errors to the global environment;
5) Updated TODO