Automatically initialize PETSc in flcbdfWrappers

* Simplify Comm init so it takes no arguments
* Assume sys.argv is default argv to pass in to PETSc
* Remove PETSc database options
* Automatically initialize DAETK and Comm/PETSc in flcbdfWrappers
* Replace DAETK-Comm with a simple Python comm
* Add some basic tests to verify Comm
* Remove Comm.init() from a few places it is no longer explicitly needed
* Replace Py_PETSC_COMM_WORLD with PROTEUS_COMM_WORLD
I'm happy to use a top-level import for petsc4py if its used in functions and pull the function-level imports out.