Fixes for yeoman generator

This patch contains changes required by `yo loopback` and fixes for bugs discovered along the way.

 - package: add mocha as dev-dep and test script
 - ModelDefinition: include `name` in the json file
 - Workspace: implement `listAvailableConnectors`
 - ModelProperty: implement `availableTypes`
 - ModelAccessControl: improve metadata providers
 - Fix serialization of Model ACLs.
 - connector: fix race condition in loadFromFile
 - ModelAccessControl: rename 'method' to 'property'
 - Fix deserialization of embedded key-value maps

/to @ritch please review
I quite like `permissions`, it was used by 2.0 workspace API.

Unless you have time to implement that change today, I am proposing to merge this PR and make the change later.

BTW to make the migration easy, LB 2.0 should support both old (`acls`) and the new property when reading config files. workspace should probably support the old name too at read-time