Switched to GSON for update checker, since Scala's JSON libs have been deprecated.
Little bit of cleanup.
Missed one.
Fixed setmetatable(t, nil), closes #464.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers
Fixes #467.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers
Update greetings.txt

was suggested on the irc
Added config entry to allow ignoring power from specific supported power mods, closes #458.
Cleaned up event listener registration a little, moving it all to init... can't remember why this was all over the place. Maybe this will break stuff.
Fixed audio tick handler never being registered.
Fixed tmp file system's usage counter not being properly reset when closed and not being recomputed on load, closes #471.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers
Giving a clearer error message if programs cannot be started because the set shell cannot be found, closes #470.
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers
Merge branch 'patch-2' of https://github.com/JoshTheEnder/OpenComputers
Cleaned up greetings.txt some more (duplicates, typos, out-of-date stuff).
Little bit of refactoring and showing the tier of item components in their tooltip if advanced tooltips are enabled (F3+H), for people that have problems distinguishing the tier by color (e.g. colorblind people).
Fixed potential NPE in server rack (since: sided fix for internal switch mode).
Merge branch 'OC1.3-MC1.6.4' of github.com:MightyPirates/OpenComputers