Documentation Updates

Proposal
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Removed `TODO.md` since all entries are either open/closed issues in GitHub (better tracking on GitHub than in a static text file) and made mention of the issues page in `README.md` so users know it exists and can better understand what we're working on

Slight modification to `README.md` for clarity

Removed Clonezilla entry in `pxelinux.cfg/default` that was accidentally entered in a previous commit