support for elements as anchors

jQuery is okay with an element object being used as a selector
this patch allows dc.js to work with elements as well as '#id' selectors
create legend skeleton
implement group naming in base and stackable charts
implement legend labels
update css for legend
add color to legend
refactor legend positioning code
fix chartBody css class name
implement legend handler on line chart
artifacts
a work branch
hack for fixing elastic binned bars
Merge branch 'fix-bar-elastic' into work
artifacts
add legend test cases for line chart
improve legend item test case
add guard to project
add legend label test case
add legend label test case
add legend mouse over for bar chart