Cleanup Yahoo, VE, Multimap layers

radical changes here. patch submitted.

the idea is to bubble out common functionality into eventpane and fixedzoomlevels layers.

this results in smaller, easier, simpler end files.

to be reviewed.

specifically,

EventPane.js, FixedZoomLevels.js should be reviewed first,

then a cursory glance at Google.js, Ve, Yahoo, MM, etc should make sense

furthermore, playing around with the examples/baseLayers.html

should be somewhat helpful.

updated patch with hardcoded resolutions arrays for 3rd party layers -- sort of negates lots of what fixedzoomlevels does... but still.

switching between baselayers (at least in baseLayers.html) seems to work now. there are still a few quirks with the multimap layer but it mostly works. we can fix that later.

please review and commit if approved

Committed as r1777.