Implemented EZP-19695: Enabling non automatic conversion of siteaccess names

Adapted the original pull request by Joaquim https://github.com/ezsystems/ezpublish-legacy/pull/465
to fit EZP-21959, only minimal changes.
Merge pull request #920 from glye/EZP-19695_sa_name_conv

Implemented EZP-19695: Enabling non automatic conversion of siteaccess n...