Some fixes and tests, begin the implementation of type inequalities solving.
Move Mvar into the core.
Cleanup, subsequent to the integration of Mvars into the core.
Intermediate commit: new unification; solves inequality constraints.
Inequalities resolution works, modulo a correctness bug.

Now one can no longer specify a special tactic for solving the TCCs but rather simply which constants to unfold. We may go back to the more general case if needed.
Corrected soundness bug in unification.
New example in top, fixed bug in inequalities solving.
Bug corrections for subtype checking. Performance acceptable.
Add a defvar construct which does not add a constant to the local context and is called by default when declaring variables using the form

x = T('x')

Where T is a type.
Various cosmetic improvements to the code.
Added color.py
rudimentary sage interface
Clean up of sage interface.
changes to support sage_interface
Merge branch 'deptypes' of https://github.com/avigad/boole into deptypes
Begin tests for sage interface.
Add unfold(name*) to conversion, add an elab function which returns the elaborated term, if there are no remaining TCCs.

Elaborate terms in the sage translator.
Clean up and devellop z3 translation. Now models are supported by Boole. Begin evaluation in boole, change defenumtype -> defenum.
Models and begin evaluation with respect to a model. Begin defining the semantics of built-in constants.
Evaluation, end and semantics of 'built-in' functions. UNTESTED!