[breaking change] Extract common code for finding org admin.

This commit moves the code to find an org admin into EcBase.  It also
removes handling for the case where no suitable admin could be found
and now just raises an error.  Moving forward without an org admin
does not seem prudent.
Move configure_chef function to ec_base
Move more common code to ec_base

Both ec_backup and ec_restore had similar initial configuration code.
This commit moves that code into ec_base and provides some additional
test coverage.  This organization is not ideal, but it will hopefully
lead to more consistent behavior between the two commands.
Merge pull request #44 from opscode/ssd/common-code-first-pass

Ssd/common code first pass