Bin module

In the Git repo, the bin folder is missing, which unconditionally prevents the framework from running, since the settings module imports bin.

Using "bin" as a module is bad as there is a builtin Python function named bin.

Second, the import mechanism is for importing code, not performing run time path resolution.

Because neither bin nor externals are provided with Git (not a problem) I hardcode their paths to the current directory, which is a reasonable & simple default when using the framework from Git, but it would be helpful for this to be done in a reasonable fashion.