PUBAPI-1234 Add snapshots to node-triton
CR updates.
- add 'triton fwrule update ID <TAB>' completion on updatable fields
- make ID arg first in ^^
- make 'triton fwrule create ...' have the rule enabled by default
- cosmetic help output tweaks
- allow 'triton fwrule update ...' to not *require* that the rule is
updated. i.e you can update just the description
Fixes#76: `triton image create ...` and `triton image wait ...`
Fixes#72: want `triton image` to still return image details even when it is not in 'active' state
