Minor style changes.
Bind data with key (username), can now remove series, code refactoring.

Code refactoring: moved update processes in dedicated functions,
function updateChart calls them all.
Add possibility of removing series by clicking on the user label
(to change).
Some problems with these changes due to data not being 'binded' by index
and not by a specific key - fixed that.
(Data is now binded to the elements by username)