Remove the ability to 'Import' .SDA files

We can instead 'Open' these files as they are just bastardized XML files.

This gets us back to a more consistent point where 'Import' gets data
directly from the dive computer (and hopefully soon we will add the
ability to load a dive directly from a uemis SDA to libdivecomputer),
and 'Open' loads a file from the filesystem of the computer we are
running on (this last sentence phrased so awkwardly as the uemis Zurich
SDA is a computer and presents a file system when connected via USB - it
just doesn't have the dive data in an accessible format in that file
system).

As a bonus we get to throw away quite a bit of code (the uemis specific
file handling, mini-XML parser with helper functions, the file open dialog
in the importer). Yay!

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

dive.h

@@ -262,8 +262,6 @@ extern void report_error(GError* error);
 extern void dive_list_update_dives(void);
 extern void flush_divelist(struct dive *dive);
 
-extern int open_import_file_dialog(char *filterpattern, char *filtertext, 
-				void(* parse_function)(char *));
 #define DIVE_ERROR_PARSE 1
 
 const char *weekday(int wday);