batch commit of arithmetic support

[jarlab-dev]

• General addition and multiplication are in place
• Most arithmetic support code has been placed in tables_ext.cpp and bdd_ext.cpp in order to minimize mess.
• There are some simple updates to the parser. Added attribute to term alu_op to distinguish between different operators without keep extending the list of basic symbols for TML (all arithmetic operators are "subclass" of ALU)
• There is much cleanup to be done, as well as improvements.
• Added couple of basic tests in tests/regression