Masked error caused by saving dbc while editor is open that causes
msg IDs to go crazy by making editor modal, but that affects all
other windows, so might be a better fix.
Added new value type of VALUE_STRING, probably better named
ENUMERATED_STRING, and it uses the table in the editor to define
the enum.
Fixed a bug in the signal viewer load when a signal is not matched
(I found it by renaming a signal and then loading)