fix not showing discover menu item

- for datasource definition types that don't support
discovery.

Fixes #330
Merge pull request #369 from strongloop/fix/hide-menu-item-on-nondiscoverable-ds

fix not showing discover menu item
Apply styles to error messages on testConnection button

- add `ui-msg-*` class set of rules for messaging
- add support for messsage response type on connection test method
- fix positioning on message
Change classes to .ui-msg-inline

These are technically inline messages, we may have a global message system soon, so I'm calling this .inline for now.