Providers authorization will only be done when needed (and independently)

[ia3andy]

Login will not be needed anymore.

Example of user flow:

1. Access launcher home
2. Click on create new app
3. Add a backend (user can now download)
4. Choose a git provider, authorize it, and select destination repo
5. Choose a cluster, authorize it
6. Launch..

The different authorizations (github/bitbucket/cluster) will be stored individually in the localstorage. The user should be able to disconnect them directly in the different hub.

Having a button in the toolbar to disconnect all authorizations at once (instead of logout) may be nice to have.