Print command flags

[Dekel Tsur]

I think that we should remove the printer flags fields from lyxrc and the
preferences dialog. Instead we will have a file called lib/programflags
that will have the flag information for various commands (dvips, dvilj4):

Program dvips
 evenpage -B
 oddpage  -A
 ...
End

Program dvilj4
 evenpage "-D2 -r"
 oddpage -D1
 ...
End

We can also use this file for storing the paper options for xdvi and dvipdfm,
which are currently hard-coded in converters.C.