GME GPX compatibility with GC.com User Routes

Changed XML header information in exported GPX file so that it can be
successfully re-imported into Geocaching.com, for use in the Caches
Along a Route feature.
Fix Hillshading tileUrl

Now that the Wikimedia Toolserver.org server has shut down, Hillshading
has to come from wmflabs.org.  Uses http rather than https because the
server's SSL certificate isn't valid for the right subdomains.
De-stringify cache labelling code.
Tabification
Added marker labels

dropMarker() now allows an optional label after the marker circle
radius. This is shown as the title of the popup when you click on the
marker.
Added postcode lookup.

Works in UK only, using data fetched by JSONP from postcodes.io.  Also
tweaked bounding boxes and associated code for checking if coordinates
are in UK (vs. Eire).
Display postcode results in a Leaflet popup.

Displays successful postcode lookup results in a Leaflet popup rather
than a Fancybox. Moved getPostcode() from GME to GME.control to allow
access to current map.  Postcode result is plotted at centre point of
postcode (up to 500m from point clicked).
Major code tidying

De-stringified the Widget code, restructured so that virtually all
injected code is held in `gmeResources.script`, and de-linted the
results.
Tidy up DOM

Avoid leaving unnecessary `<script>` elements in the DOM after script
insertion or JSONP / XHR calls.
Revert "Tidy up DOM"

This reverts commit 737357f44547557f9843417cd345d8402ab4bda8.
Tidy up DOM

Avoid leaving main script in DOM after insertion.
Freemap.SK support

Added Freemap.SK Slovak OSM map sources to the default list (not
selected by default).
Improve Google keyword search

Update Google search URI to get more hits on caches, by including pages
that were indexed with an old-style address.
Fix Unicode handling

Use `encodeURIcomponent()` on cache data before base64 encoding, as
base64 can't handle Unicode characters. Should mean display of waypoints
and corrected coordinates is fixed for caches with extended characters
in their names.
Improved initialization code

De-stringified page-specific script fragments and put them in
`gmeResources.script`.
Removed duplication and simplified the `switch(gmeResources.env.page)
{}` section by creating a `buildScript()` function.
Geograph bugfix

Avoid making bad API call for German Geograph images.
Version 0.7.1.2

Version bumped for review.
Waypoint display zoom level improvements.

Improved `GME_displayPoints()` to make zooming behaviour more intuitive
when displaying waypoints.  On a listing page or when clicking through
to the main map, the map will be zoomed to display all the points, but
no further than level 15 when the points are close together.  This now
includes the primary point, even if GME doesn't draw a marker there.
When dragging'n'dropping, GME maintains the current zoom and just pans
to the centre of the dropped coordinates.
Searchbox improvements

Added radius to Plot function to allow plotting circles at specific
coordinates, rather than just points.
Improved keypress event handling to allow searching by pressing enter in
search box.
Updated URL for Leaflet API documentation