Added comments explaining events and configuration parameters to
interactions.
modified enableInteraction and disableInteraction in ViewerBase to use
the new interaction classes.
Merge pull request #7 from IDgis/interactions-improvements

Interactions improvements
- Added getServiceLayer call to MapProvider
- Symbol controller looks up service layer and service type
Merge pull request #8 from IDgis/legendsymbols

- Added getServiceLayer call to MapProvider
Merge remote-tracking branch 'origin/master' into toc-symbol
added functiom getLayerById
parse initialExtent from configuration
introduced onlyOneActive
added getInitialExtent
- made toc working
- use getMapById
- query voor SpecialIdentify
no symbol in defaultLayer TOC
Symbol class with id
setSymbol for the time being with servicelayer id as id
included Symbol in view
revert TOCItems for display
corrected typing error
ol2 - > ol3
added getScaleForExtent, getters and setters for UnitsPerPixel
added getScaleForExtent