Refactoring (in paticular for LineChart) + added Renderer + LF
normalization
refactored line renderer + bar renderer
refactored barchart and linechart
Merge branch 'refactored-linechart'

Conflicts:
	gwt-d3-api/src/main/java/com/github/gwtd3/api/core/Formatter.java
	gwt-d3-api/src/main/java/com/github/gwtd3/api/scales/LinearScale.java