add export->"save geojson as gist" mode with "edit in geojson.io" link :)
geojson export tweaks:
* omit "relations" property from exported geojson if there are none
* use a concatenated id property instead of two columns for osm-type and osm-id
more robust i18n loading (failed in chromium when loading from a local file system)
save as gist also for packaged index
open gist and geojson.io links in new tabs
add "rel" (shortcut for "relation") to syntax highlighting.
finalize multipolygon rendering

handle multipolygon outlines analogously to untagged way-nodes if
they do not contain tags other than the mp-relation (for outer
lines) or do not contain interesting tags at all.

this also fixes the incorrect duplicate polygon rendering in the
case where an outer line contains polygon-like tags that should
only be tagged on the multipolygon

see #22
update tests and add a rather complex multipolygon test scenario
drop mp_outline flags from mapcss and exported geojson

see #22
improve simple polygon test case
fix bug with simple multipolygon rendering
harmonize colouring of simple/normal multipolygons:

show them all in the "relation member" colour, for consistency.
include "anonymous" gist user for geojson.io links
special handling for global bbox in xml queries

global bbox parameters in xml queries uses an OverpassQL-like
notation instead of n/s/e/w parameters. This needs special
treatment to not create invalid queries. Introduced some regex
magic for this.

Example:
  <osm-script bbox="{{bbox}}">
becomes
  <osm-script bbox="1,2,3,4">
expose codeEditor for better testability
add tests for query expansion
fix "empty dataset" detection for the case where only <bounds> are returned
do not list templates in save dialog combobox
fix "huge_data" dialog that was hidden by the "loading" overlay.
allow empty template parameters