Refactor command line parameters

[nickng]

Move test helpers to its own package so base don't pull in testing and hide command line parameters from test parameters.
This change also make -h more useful, showing all the different modes of input (FG/FGG/internal/inline)

Usage:

	fgg [options] -fg  path/to/file.fg
	fgg [options] -fgg path/to/file.fgg
	fgg [options] -internal
	fgg [options] -inline "package main; type ...; func main() { ... }"

Options:
        ....