Set the role id to be generated

See https://github.com/strongloop/loopback-connector-postgresql/issues/5
Add a test case
package: the next version will be a minor version
Merge pull request #254 from strongloop/feature/role-id

Set the role id to be generated
Fix a slowdown caused by mutation of an incoming accessToken option.
Merge pull request #341 from STRML/fixAccessTokenMutatedOptions

Fix a slowdown caused by mutation of an incoming accessToken option.
Remove relationNameFor
Update juggler dep
Merge pull request #342 from strongloop/feature/refactor-relation

Upgrade to loopback-datasource-juggler 1.6
Merge branch 'master' into 2.0
Merge branch 'master' into 2.0