added sim init restart tests and fixed bugs found by it.

* Added restart test that checks for expected vals of context's sim info,
  time, etc.

* sim init tests remove any potentially existing test db file at beginning of
  setup.

* Timer checks if there is a branch time, if so, sets the initial time_ to be
  it.

* context InitSim method now properly assigns the passed SimInfo to its
  internal sim info var.