move optional command prefixing out of con_tty and con_curses to a later shared point

Main intended change is to carry the information of the commandprefix's existance on to a later location in the code
and to not add an enforced prefix anymore to history if it wasn't used

Unintentionally the whole thing should now also enable the win32 console to do the same.
adding com_consoleCommand which sets the default command that gets used for text entered into the consoles
this works for ingame as well as outgoing consoles

an empty value will make all entered texts executed as commands direclty
by default it's set to "say" for the client and is empty for the dedicated server
add a few lines of documentation to com_consoleCommands code
Merge remote-tracking branch 'upstream/master' into feature/com_consoleCommand
prepend commandprefix to history again, if com_consoleCommand is empty and thus sets the console into command mode
let the ingame console use its own cl_consoleCommand, so users can adapt the behavior of consoles separatly
remove default say for terminal consoles making them run commands directly again
let also the ingame console and the tty console prefix with a escape if it was in direct command mode
Merge pull request #168 from t4im/feature/com_consoleCommand