Deprecate usage of system_setup_block

This deprecates the usage of system_setup_block in favour of before :suite.
Docs are updated and we now through a deprecation message. I've also added
tests for before :suite and the legacy methodology.

Signed-off-by: Ken Barber <ken@bob.sh>
Rename old helpers to shell, node, rcp

This patch renames all the helpers to smaller names for simplicity, updating
tests and docs to reflect the new names. Also deprecation warnings have been
added.

Signed-off-by: Ken Barber <ken@bob.sh>
Merge pull request #17 from kbarber/match_sugar_pre_work

Renames and deprecations, in prep for increased sugar