Change the paths generator to prevent invalid paths from being used

[uglow]

• [x] The paths generator should not allow the following:
  • blank path values (except for the modulesDir)
  • paths that contain ./
  • paths that start with '.' or path.sep. Only relative paths can be used
• [x] Use path.resolve() instead of using '/' for path separators see here
• [x] Each time the paths generator is run, it should check that each path is valid. If not, it should re-prompt for valid paths.
• It may not be possible to verify these paths:
  • the output.reports path, because it probably won't exist while Mocha is still running
  • the output.devDir and output.prodDir path, as the project may not have created these when the test is run

[uglow]

Closed by f8591181ffc913c967a4df7700cd0faf94bea371