root_paths redesigned for clean importing

Now there's a clean separation between build script
file names and the projects contained within them.

The root_paths APIs are now purely focused on importing
files without regard to whether there's a project,
or simply further import_subdir (or similar) calls.
import_subdir.* now take an altPath argument
Moved code import statements into test2 module
documented repo.import*

Updated readme and manual.

Minor rename of import functions.  Refactored
remake and sub-files to be hae more idiomatic
use of import_file/import_subdir
refactored currentScriptPath logic