make sure we pull the new version of Mockingbird Toolbox;
this version exposes the MBModule's moduleEnvironmentFilename hook
make it possible for MBModules to specify their own environment files

this means it isn't necessary to implement an environment loader to do this
move responsibility for the auto-loaded environment file

from MBVariableSpace to MBDataEnvironmentModule
and rename the file accordingly
use newer MBToolbox to get MBModule updates