Added multi-delete for git-delete-branch and git-delete-tag

In order to more efficiently delete multiple branches and tags, I updated `git-delete-branch` and `git-delete-tag`. In this PR:

- Updated `git-delete-branch` to accept multiple branches
- Updated `git-delete-tag` to accept multiple tags
- Updated documentation to match changes
- Fix for documentation of `git-delete-tag` (said `branch`, corrected to `tag`)