Remove pointless IUSE=optimizations

All it does is toggle -O0/-O2 in the default build.
Fix "useless 'dodoc COPYING'" repoman warnings

I suppose it makes sense; your package manager requires you to be aware of the
license *before* installation.
Correct dev-libs/boost dependency

Apparently there's no IUSE=test on that, so this never would've worked.
Remove gentoo-added "emake -j1"

s6 seems to force a serial build internally anyway. Successfully build-tested
with "emake -j80 -l".
Fix all errors and warnings reported by `repoman`

  - Every package has proper metadata.xml files now
  - `minecraft-server-*.ebuild` gained a proper license file
Patch c10t to re-enable -n/-H options

This should go upstream at some point, can't be bothered today.
Remove lingering mentions of the tmux code
Add some extra content to the metadata files