Added unit test for ApiClient.load()

This is failing as it doesn't properly load all fields from the JSON
response
Delegate ApiClient.load to ApiClient.json_create

This means the validator/public_key/admin fields of the ApiClient
object now get set properly
Add --validator option to create validator client via knife

Also update tests to check the defaults for admin/validator
Add a --force option to protect against accidental deletion of validators

It's hard to recover an org from having a deleted validator client -
this patch protects against deleting validator accidentally e.g. in a
for loop around knife client delete by requiring you to specify --force

Includes specs around this new functionality
Merge pull request #1272 from opscode/jc/OC-130/knife-delete-validator

Add a --force option to protect against accidental deletion of validators
Merge pull request #1270 from opscode/jc/OC-130/knife-create-validator

New command line option for knife client create to create validator
Merge pull request #1269 from opscode/jc/CHEF-5047/client-show

knife client show does not show validator/admin correctly