in rewrite: support user specified formats

[sckott]

from @jhollist

40 25 5.994, but represented as 40.255994. Looks like dd, but is dms

Not yet in rewrite allowing user formats, but will try soon, and should in theory handle the above

[sckott]

for formats could follow what CLongLatString does:

%H - hemisphere - single character of N,S,E,W
%C - integer co-ordinate, may be negative or positive
%c - decimal co-ordinate, the entire co-ordinate,
         may be negative or positive
%D - integer degrees, always positive
%M - integer degrees, always positive
%S - integer seconds, always positive, rounded
%d - decimal degrees, always positive
%m - decimal minutes, always positive
%s - decimal seconds, always positive
%% - for %