feat: add a little ROOT

[baltzell]

Copied from Andrey's https://github.com/drewkenjo/j2root, just histograms for now. Requires root-config and scons in path (hence the failing CI tests currently), should switch to cmake? clas-io currently doesn't build from within netbeans.

To-Do:

• Required:

• automatically (and manually) disable C++/ROOT in maven build if support not found
• runtime must only require ROOT support if used
• add a dedicated CI test (github or gitlab)

• Desired:

• auto-detect C++/ROOT/scons/gcc support for a user-friendly error
• Netbeans integration (currently not runnable)
• consider replacing scons with cmake or other