Invoke command on one of multiple connected SDMs without error

[jessitron]

we could provide a --sdm top-level option, so like atomist --sdm MyFavoriteOne run thingie

note that SDMs need to have names which they need to have anyway if we're going to display them decently in show skills everything needs a name

[johnsonr]

1. Start embedded SDM via create sdm, choose spring
2. Have sample SDM running
3. Type atomist show skills

Output will include describe sdm bootstrap describe sdm SelfDescribe Describe this SDM

Typing either describe sdm command produces no output