Allow loading modules from sources

[melkyades]

Currently, the only way to load modules is to read them from image segments.

In order to do so, the programmer has to open the pharo boostrapper, load the module there and write it to an image segment.

This process is cumbersome and should not be needed.

Instead, the system should by default load a source module loader, which is capable of reading the module from tonel sources (as well as other formats), and installing it into the system.

After loading a module from sources, the system will write it as an image segment automatically, so that next time the thing is ran it is not necessary to compile stuff.

The JS platform more or less supports this through ModuleImporter module, we just need to plug the existing things to make it work in C++ vm too.