Switched from optparse to argparse.

Now use subcommands including the core 'deploy' subcommand. Refactored
testing code to accomodate argparse. Cleanup to parser tests and help
output.
Removed gitrepo deploy flag.

The gitrepo flag can only be used in an environment in which Git is installed.
This makes git a dependency of SALVE, which it should not be. Instead, after
SALVE has a plugin framework, there is a possibility of a git plugin that allows
the specification of Git blocks.
Merge branch 'feature/use-argparse' into dev
Converted common options to globals.

Instead of being overridden by block settings, the globals are applied
over all of the block-specific values. Alterations to tests support the
change.
Merge branch 'refactor/global-config-values' into dev