Add Developers' Documentation

[vgvassilev]

We should add some developers' documentation on how to start development in the project locally. I believe a lot of the folks with clang-repl background will have trouble set up the infrastructure locally allowing them to add improvements.

[SylvainCorlay]

Is the information to install from source insufficient?

[vgvassilev]

It is sufficient to build it, however, if you want to start hacking it is not. For example, I think we need to explain how to set up a debug build, and how to configure gdb to be able to debug the already spawned process from jupyter. There were a few gdb tricks one needed to do.

[vgvassilev]

@tharun571, could you take care of this issue? You seem to gone through that process recently?

[tharun571]

Okay, will do. I'll add the debug documentation.