Contactgroup Configuration

[nilmerg]

Goal

We need a way to configure contactgroups in the UI.

How it Should Work

• A tab in the Configuration menu section should lead to a list of contactgroups
• This list allows to paginate, limit, sort, search for and create contactgroups
• The button to create a contactgroup should be on the top left of the list
  • Clicking on it, opens a modal which allows to choose a name and define the group's members by using a TermInput
  • Saving closes the modal and shows the group's detail in the right column
• A click on a list item opens up a detail on the right, showing the name of the group in the header
  • A button on the name's right side allows to edit it
  • The modal should be the same as when creating a group, plus a remove button
• The detail's content lists a group's members, clicking on such an item leads to the contact's configuration view

[ncosta-ic]

I might consider updating the ContactGroup class once Icinga/icinga-notifications#187 gets sorted out.
It currently links to the contactgroup table and this implies a class name of Contactgroup, which seems wrong.