Mixed case system commands

[Waldek Hebisch]

Currently code handling system commands tries to support mixed
case command. This does not look entirely consistent and is
different than rest of FriCAS which is case sensitive.
I consider removing this and accepting only lower case commands.

Opinions?

--
Waldek Hebisch

[Ralf Hemmecke]

No particular. Using system commands touches me only (and only rarely)
through MoreSystemCommands. In a session I always use lower case.
Go on.

Ralf