[FEAT] Admin rights to make changes to created persons and to delete persons

[radoman2]

Sometimes users make wrong entries when creating new persons (such as wrong name or index number), also double entries happen. The feature requests adds admins the ability to correct these.

[aleksasiriski]

Related to #97

[aleksasiriski]

@GrbavaCigla Any chance we get this feature in the coming days? Since the beginning of your PR we have created an one-login admin page that creates an admin session so this should make things simpler for you