Save proofs (#187)

    -Add ids to terms like for formulas
    -Add serialization of proofs. Theorems can be serialized to binary files and loaded back on later run.
    -On my machine, running everything up to Recursion.scala takes 19s instead of 24s.
    -Does no hash consing, but simple optimizations to proof size (remove consecutive rewrites, flatten subproofs)
    -Cleans up the distinction between fullName (with the whole path, should be unique) and name (just the last part, possibly duplicate across different files/domains).
    -Good completion of documentation in WithTheorems
    -checkProofs does not print proofs of more thant 100 steps now.
    -fixed an indexing bug in ShrinkProof.flattenProof
    -Suite of tests for serialization, export then load a collection of theorems.
    -Push suite of tests for Tableaux tactic that were missing.