Support bulk installing of GitHub plugin

[ccverg]

Allow batch editing of plugins from /tools:

• Add checkboxes next to all user/orgs that will add all projects associated with that user to the "Batch edit"
• Add checkboxes next to all projects to allow individual selection of projects to add
• Update the right-side content with a "Batch editing" notice, including a full list of all projects to be edited
• After editing, list each changed repository in a success message

Quick mockup:

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[davidhtien]

Could there possibly be a more complete mock up of what you guys want this to look like? I'm confused by what the batch edits on the right should be, how come there's no button to install or save and all the options that are available for a single selection disappear? Also how would you handle selection of multiple elements in different states, such as in the picture provided of one that is not yet installed and one that has already been installed?

[ybouhjira]

@davidhtien I think I've already handled that issue in my PR now we are waiting for a backend change so that the changes could be that with one request to the API.