red-brick/npw: Move nextId logic from pages to wizard

Makes pages easier to reuse.
red-brick/npw: Move page title step prefix to wizard

Makes pages easier to reuse.

Also don't refer to the program being defined as the "new" program.
red-brick/npw: Reduce inter page dependencies

Access available files and directories via the wizard.
red-brick: Cache unicode version of REDString data
red-brick: Add helper methods in between program callback signal emissions

This works around a segfault in pyqtBoundSignal_emit.