Added support for having the same person in multiple instances, #199

Before personal_id was treated as unique but now the composite key of
(personal_id, instance_id) will be treated as unique. This allow
students to exists in multipe instances (schools).
Merge branch 'duplicate_personal_id_199'
Fixed problem with duplicates suites, #203

Overlapping roles (suite_member and
suite_manager) that result in duplicates suites in the suites listing
for some users. This fix adds a contraint to only fetch unqieue suites.

The reason why some user get muliple and overlapping roles still needs to be
addressed for verifying that this behaviour is OK.
Merge branch 'duplicate_suites_203'