Pass Github call to GraphQL

[Ludovic Gonthier]

Description

The objective of this issue is to reduce the number of calls done to the Github API.
The best way to do that is to make use of GraphQl.

GraphQl queries:

• Query to fetch pull_requests with OWNER affiliation (My repository menu)
• Query to fetch pull_requests with COLLABORATOR affiliation (Contributing to menu)
• Query to fetch organizations (organizations sub-menu)
• Query to fetch open pull_requests from the selected organizations

Doing this, there is no way to fetch repositories by their teams.
To get over that, the user will have to choose which repository he wants to watch on a list. (A new dropdown or tanking the place of the teams sub-menu)
The choice of repository being watched will be stored in the local storage to avoid to re-select repositories on every refresh.

current limitation: The API Rate Limiting on the GraphQL API is of 200 calls per hour.