[UI][Dashboard] add/remove dashboard objects

[brylie]

Story

As an API Manager
I would like to choose which objects (charts) to display on the dashboard
So that I can display information deemed important to my organization

Example

I decide that the following information is important to monitor

• API Response time
• Geographic locations

So, I click a button, such as Add Dashboard Object, and choose the object type from available objects. The object is then added to the dashboard.

Related issues

Parent: #62
Sibling: #70