update to 'Fix google map offsets in china'

[johnd0e]

Misc updates for #68.

fix-china-map-offset: Baidu support

• Sources refactored to be closer to upstream https://github.com/Artoria2e5/PRCoords
• Baidu support
• Clarify comment about usage

...and more:

• applied to googleMutant
• fix filename

[johnd0e]

Todo:

1. applied to googleMutant

   Perhaps it wasn't necessary and should be reverted.

2. options for HongKong...

   It seems that it needed for Baidu only.
   If we could make plugin for Baidu it would have sense.
   But I'm not sure.
   (If not than this could be removed)

3. ...and map type

   We need to test different maps.
   Perhaps this required for Google only, so condition need to be enhanced.

4. It also possible that we do not need check 'if in China' for every Chinese map.
   Need more maps' plugins to test...
   BTW, leaflet has interesting function, that allows to simplificate our polygon, like here: http://mourner.github.io/simplify-js/

5. (redefine leaflet methods cleaner)

   I suppose that we can make it even cleaner, not touching L.GridLayer.prototype.
   Will try tomorrow.

[johnd0e]

I think that better leave boot.js untouched and patch layers options in plugin setup instead.
All layers are accessible via layerChooser._layers, and it's easy to patch only _mutant layers.
Will try tomorrow.

[johnd0e]

@modos189
I need an advice.

Currently we rewrite L.TileLayer class:

  L.TileLayer.include(fixChinaOffset);

A more proper way would be to extent it with new class:

  L.TileLayer.GCG02 = L.TileLayer.extend(fixChinaOffset);

And then instead of needFixChinaOffset option we would use that new class:

var mapLayer = new L.TileLayer.GCG02 (url, options);

But I doubt that we should make things more complex here..

[johnd0e]

@modos189?