#1 Boolean operations

[Larry Smith]

bool helper functions (define these, from python:
union = operator|, intersection = operator&, difference = operator-)
use vector<int> and Hash args
IntHash bool(A, B) where A, B can be any combination
of int (for a singleton), vector<int>, or IntHash.
Implementation uses IntHash.
since name is generic, users may need to say
tMine::bool. Also, define operator&& as inline for and, etc.
can you ever say operator"union"?
Question: should we also implement a CharVec flag intermediate?