Rework editbox history to be per-frame.
Based on code suggested by Torhal (perhaps from CrappyChatFix), but uses the
updated command history supplied by the history module
Handle empty cmdhistory in already pushed code
reverse up and down meaning in chat command history
Hopefully fix an outstanding bug in TellTarget module.  Use UnitRealmRelationship("target") ~= LE_REALM_RELATION_SAME instead of UnitIsSameServer("player", "target")
no not! from prev fix