Add ROOT files support

[calvellido]

ROOT is used by almost all experiments throughout High Energy and Nuclear Physics to write, read and analyse data. ROOT provides a machine-independent compressed binary format, including both the data and its description. ROOT files can be structured into ‘
directories’, exactly in the same way as an operating system organizes the files into folders. ROOT directories may contain other directories, so that the structure of a ROOT file is more similar to that of a file system rather than to an ordinary file [1].

The JSROOT project intends to implement ROOT graphics for web browsers. Reading of binary ROOT files is supported [2].

Adding ROOT files support to DPMbox might be very useful and it be achieved through the JSROOT project.

[1] ROOT I/O in JavaScript: http://iopscience.iop.org/article/10.1088/1742-6596/396/5/052011/pdf
[2] JSROOT: https://github.com/linev/jsroot