Introduce new way of dynamically specifying environment paths in the config.inc.php file.

All hard-coded paths shall be replaced using this infrastructure. Currently BRAINSFit and fyborg use it.
Add support for commandline access of plugins by calling $ eval `php env.php` to setup all environment variables.
Setup environment when launching a plugin.

Also, convert ResampleScalarVolume to use the dynamic environment.
Add almost all plugins to the dynamic environment setup.

Not finished yet: Connectome and fcMRI since weird paths.
All plugins but the connectome plugin are now completely dynamic.
Remove obsolete files.
ENV_SLICER_DIR points now to the real Slicer directory and not the lib.
Check if CHRIS_PACKAGES is setup.

When using set_status.php the env.php gets included but is not setup correctly which is fine but prints some warnings and errors.
Use CHRIS_MAIL_SUFFIX from the config file when creating new users.
Merge branch 'dynamic_package_paths'