NXCALS-3488 Variable lists

#Merge request template @acc-logging-team - please have a look for approval.

domain:

1. Visibility is an enum that allows us to hide objects from users:

• Public is querable for all
• Protected is querable by the owner
• Private is not querable.

2. Group now has visibility property, as well as creation time (as required by backport-api)

server-side:

1. GroupService this handles all the CRUD for Groups, but it does not manage visibility, accessibility etc.
2. SecureGroupService this is a decorator over GroupService that encapsulates all of the simple security logic we are required to have. It's easy to detach once we have a more robust user/credentials/permissions management. Feel free to suggest a better name!
3. GroupController now only uses the Secure version of the service.

client-side:

1. GroupService CRUD methods now made public.

backport-api:

1. Group -> VariableList conversions
2. implemented getVariableListWithName
3. implemented getVariableListsOfUserWithNameLikeAndDescLike
4. implemented getVariablesOfDataTypeWithNameLikePatternInVariableList
5. implemented getVariablesOfDataTypeInVariableList

Closes NXCALS-3488