Tidying up of newstart.rst and fifo.sv to include as much code as possible by reference.
Should reduce repetition and make it easier if changes occur in source.
Primarily addressing Nak's comments on the PR first.
Of note is the change from separate files to a single file.
Changed to boolector engine and bmc by default.
Updated install instructions to move z3 to optional and boolector to
recommended.
Literal code includes use :lines: option.
