Began implementation of Representation Theorem.

First step: all queries are nested within K_k or B_k.
Fixed: compiler errors due to -D_GLIBCXX_CONCEPT_CHECKS.
Continued implementation of Representation Theorem.

* Implemented ||.|| operator in Formula::Reduce().
  Beliefs not yet implemented, possibly needs API changes.
* Removed Term::Factory arguments from Formula::[Eval|AddToSetup[s]]().
* Added StdName::SortedSet::WithoutPlaceholders().