Added sf\3tshell platform with support for building beagle textshell+fshell ROMs.
As part of that:
* Added baserom command and tweaked it to be more friendly with SF baselines.
* Lots of build fixes
Also cd now makes sure the current working directory matches the file system with respect to case.
These two executables exists to allow fshell to eclipse the ROM based "econs.dll". This can't be done
within the .SIS file because the app installer doesn't allow ROM files to be eclipsed.
fshell_inst.exe copies "<install_drive>:\sys\bin\iocons.dll" to "<install_drive>:\sys\bin\econs.dll".
It is launched by the tool-kit .SIS file at install time.
fshell_uinst.exe deletes "<install_drive>:\sys\bin\econs.dll".
It is launched by the tool-kit .SIS file at uninstall time.