Consolidate SolverTerminationType enum.

1. Rename SolverTerminationType to TerminationType.
2. Consolidate the enum as
  a. CONVERGENCE - subsumes FUNCTION_TOLERANCE, PARAMETER_TOLERANCE and GRADIENT_TOLERANCE
  b. NO_CONVERGENCE
  c. FAILURE - captures all kinds of failures including DID_NOT_RUN.
  d. USER_SUCCESS
  e. USER_FAILURE
3. Solver::Summary::error is renamed to be Solver::Summary::message, to both
reduce confusion as well as capture its true meaning.

Change-Id: I27a382e66e67f5a4750d0ee914d941f6b53c326d
15 files changed