feat(layout.util) Add border and background color settings to the layout manager
docs(layout.util) Adds inline documentation
tests(layout.util) Adds tests for the border and background methods
style(layout.util, layout.layoutManager) Removing the underscore for private functions
feat(d3-ext.border, d3-ext.backgroundColor) Adds border to d3 selections
style(d3-ext.background-color) Renaming files
test(d3-ext.size) Adds test to verify that rect is added only once.
refactor(d3-ext.border) Refactoring the getStrokeDashArray method
refactor(d3-ext.backgroundcolor.js) Refactoring the working of background-color
doc(d3-ext.background-color) Adds details documentation.
test(d3-ext.border) Adds test to verify only one rect is appended