showing overlay info at mouse position
layers now can implement the queryLocation method
fixed mouse up/down mixup
respond to map queries through events
removed debug messages
Final touches on the mouse info / location querying.

- renamed mouse-to-world method to displayToMap()
- mouse coords are obtained through canvas.relMuoseCoords()
- map positions are now type-less XY tuples
- coordinate system conversions are not hard-coded anymore
  (although the OSM map itself is hardcoded)
fixed places where event.page{X,Y} were needed
Fixed long indentation
Fixed logic for setting defaults via option
Fixing very minor style issues
Added methods to convert between latlon to merc vv
Using added proj4 mercator methods for conversions
Fixed document
Display to map should return coordinates in display gcs

Also when query, convert from display gcs to actual gcs. When
we add a layer to the map we already convert the data into
map gcs. So layer should be be able to find the data using the
map gcs. In the future we may revisit this though
Got locations pretty close to google maps
Merge remote-tracking branch 'origin/77-show-mouse-info' into next

* origin/77-show-mouse-info:
  Got locations pretty close to google maps
  Display to map should return coordinates in display gcs
  Fixed document
  Using added proj4 mercator methods for conversions
  Added methods to convert between latlon to merc vv
  Fixing very minor style issues
  Fixed logic for setting defaults via option
  Fixed long indentation
  fixed places where event.page{X,Y} were needed
  Final touches on the mouse info / location querying.
  removed debug messages
  respond to map queries through events
  fixed mouse up/down mixup
  layers now can implement the queryLocation method
  showing overlay info at mouse position