Support bulk installing of GitHub plugin

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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