Resonator on map
Change:
Add "RESONATOR_DISPLAY_ZOOM_LEVEL" to control minimum zoom level resonator will display
Add layerGroup "resonatorsLayers" to draw resonators on it.
Add "window.resonators" to store references to resonators on map

Resonator will have guid of portal with ".11" or ".12" replaced with ".r0"~".r7"
Add function "window.renderResontor" to draw resonators (use sorgo's code [sorgo](https://github.com/sorgo))
"window.renderPortal" will call "window.renderResontor" before add portal to portalsLayers
Change "window.removeByGuid" to handle resonators
Change "window.cleanUp" to handle resonators cleanup
Move resonator layer back to layerGroup "portalsLayers",
to make it work with portal level filter.
And modify cleanup code to work with this change.
Code cleanup and minor change
Change:
Code cleanup
Loop over all portalsLayers when delete resonator
Resonators deletion of portal move
Move Resonators deletion to 'remove' event of portal
Resonators deletion of zoom level move
Change:
Move resonators deletion to 'zoomend' event of map.
Some clean up of code.
Change guid format of resonator
Change:
Guid format of resonator change to following,
[portal guid]-resonator-[slot]

Some code cleanup
Comment correction
Correct comment of "portalResonatorGuid"
Add contributor
Add [sorgo](https://github.com/sorgo) as contributor for his rendering code.
Change resonators render min zoom level and radius
Change:
Resonators render minimum zoom level 16 -> 17
Resonators render radius 4 -> 3
Some cleanup and performance tuning
Merge pull request #78 from Xelio/patch-map-resonator

draw resonators for each portal on map for high zoom levels (17+). Patch by Xelio.