remove gpx reader support for probelmatic extensions. (#1198)

1. groundspeak is generally used with gpx 1.0.  Our attempt to
support it with gpx 1.1 required schema violations.

2. opencaching.de no longer uses the geocache element.  Our
implementation required schema violations.

gpx.cc

@@ -1033,6 +1033,7 @@ GpxFormat::qualifiedName() const
     {"http://www.garmin.com/xmlschemas/GpxExtensions/v3", "gpxx"},
     {"http://www.garmin.com/xmlschemas/TrackPointExtension/v1", "gpxtpx"},
     {"http://www.groundspeak.com/cache/1/0", "groundspeak"},
+    {"http://www.groundspeak.com/cache/1/0/1", "groundspeak"},
     {"http://humminbird.com", "h"}
   };
 

gpx.h

@@ -326,9 +326,7 @@ class GpxFormat : public Format
   {"/gpx/metadata/" name, {type, false}}
 
 #define GEOTAG(type,name) \
-  {"/gpx/wpt/groundspeak:cache/groundspeak:" name, {type, true}}, \
-  {"/gpx/wpt/extensions/cache/" name, {type, true}}, \
-  {"/gpx/wpt/geocache/" name, {type, true}}	/* opencaching.de */
+  {"/gpx/wpt/groundspeak:cache/groundspeak:" name, {type, true}}
 
 #define GPXWPTTYPETAG(name,type,passthrough) \
   {"/gpx/wpt/" name, {type, passthrough}}, \
@@ -366,18 +364,14 @@ class GpxFormat : public Format
     GEOTAG(tt_cache_difficulty, "difficulty"),
     GEOTAG(tt_cache_terrain, "terrain"),
     GEOTAG(tt_cache_hint, "encoded_hints"),
-    GEOTAG(tt_cache_hint, "hints"),	/* opencaching.de */
     GEOTAG(tt_cache_desc_short, "short_description"),
     GEOTAG(tt_cache_desc_long, "long_description"),
     GEOTAG(tt_cache_placer, "owner"),
     GEOTAG(tt_cache_favorite_points, "favorite_points"),
     GEOTAG(tt_cache_personal_note, "personal_note"),
     {"/gpx/wpt/groundspeak:cache/groundspeak:logs/groundspeak:log/groundspeak:log_wpt", {tt_cache_log_wpt, true}},
-    {"/gpx/wpt/extensions/cache/logs/log/log_wpt", {tt_cache_log_wpt, true}},
     {"/gpx/wpt/groundspeak:cache/groundspeak:logs/groundspeak:log/groundspeak:type", {tt_cache_log_type, true}},
-    {"/gpx/wpt/extensions/cache/logs/log/type", {tt_cache_log_type, true}},
     {"/gpx/wpt/groundspeak:cache/groundspeak:logs/groundspeak:log/groundspeak:date", {tt_cache_log_date, true}},
-    {"/gpx/wpt/extensions/cache/logs/log/date", {tt_cache_log_date, true}},
 
     {"/gpx/wpt/extensions", {tt_wpt_extensions, false}},