New "options" treatment in the D-Bus API.

- A "options" argument is now intended to pass additional options to
  the lvm2 commands that are spawned.

- Some arguments like extent size and stripe configuration
  should be done with options, but have been removed for now.

- The "wipe" option is now passed as a regular argument.

Closes #8

Signed-off-by: Stef Walter <stefw@redhat.com>