Added capabilities to organize and manage lines.

Hy,

I use your library for a little side project and added some capabilities to organize and manage lines.
I needed to change the order of the lines so i added _LineChartView.swapLines()_. I also needed to identify a line in the _OnPointClickListener_ so I added a _mName_ field to _Line_.

Greetings,
Fabian

Ps:
Could you please add a licence file to the project?