Improvement of main menu - colored items

[eugensyl]

Main menu can have colored lines:
- gray - for unavailable/unknown commands (as now Disconnecting FTP) even user defined commands
- blue - for user commands em_xyz (not internal commands)

[m^2]

Main menu can have colored lines:
- gray - for unavailable/unknown commands (as now Disconnecting FTP) even user defined commands

One can dynamically change the meaning of an internal command. TC couldn't detect such changes w/out performance loss and it would be annoying to see a command greyed out because at TC startup it was unavailable. Also, it might increase startup time when user has many commands in the menu.