Revert "Trying to get rid of `FMLCommonHandler.instance.getEffectiveSide` where possible, since it can apparently fail in some scenarios."

This reverts commit b3813bc4f563a4066fd79db1dad16db3673bb324.

And a few more related commits. Turns out this was caused by some Bukkit plugin, tho it is still unknown which one exactly.

Conflicts:
	src/main/scala/li/cil/oc/common/EventHandler.scala
	src/main/scala/li/cil/oc/common/component/TextBuffer.scala
Centralizing use of sided checks to make it easier to swap out for testing in the future, and added some hackiness to maybe make it more stable.