Fixup logic minimization error handling
Simplify some PicoSAT constant values
Cleanup some espresso constants
Use functools/operator to cleanup bitvectors
Cleanup of BitVector types

* BitVector is now immutable
* Using EXPRZERO/EXPRONE instead of 0/1
* Raise vexpr coverage to 100%
* Use X + Y to concatenate
Add shift operators to BitVector
Get rid of unused import
Get rid of redundant boolify utility function
Fix inconsistency with uint2bv(0)
Add Espresso script and PLA parsing utility