Remove unused URLs for other themes other than CERN/base

Based on the value of the CAIMIRA_THEME environment variable, the list of available urls will change:

• If None is declared, the url list remains as before;
• If caimira/apps/templates/cern is declared, the url list remains as before;
• Any other value will result in a reduced url list: home, form, static files and report.

It is possible to define any generic page via the EXTRA_PAGES env. variable, as detailed here.

Given that the logic for the urls changes, the /about and /calculator/user-guide urls will be in the default list, and not defined by the EXTRA_PAGES variable, which is the empty list by default.

assigned to @lrdossan

approved this merge request

mentioned in commit dad34cde

merged