Currently each entry must be a single line of text. This results in long lines, especially on the RHS.

I have experimentally inserted a transformation of the DSL text (in DSLTokenizedMappingFile)
which converts '\'+EOL on the fly to a space. (The passed-in reader is read into a buffer, '\'+EOL
is translated to space, and EOLs are inserted later to readjust the line number.) In a text editor,
I can now write, e.g.,

then][][Bb]ook the customer for the flight=\
$f.setAvailable( $f.getAvailable() - 1 );\
update( $f );                            \
Booking booking = new Booking();         \
booking.setCustomer( $r.getCustomer() ); \
booking.setFlight( $f );                 \
insert( booking );

Of course, the DSL editor will not preserve this, but future development might provide more
convenient editing there, too.

Any objections?
-W