Move serializers only used by gregui.

It has been decided that a sponsor at a unit should have access to all
roles at that unit. This includes all units accessible through
hierarchical access.

Resolves: GREG-150

Serialization has been moved to serializer classes, sharing them when
sensible and Views have been converted to ViewSets to simplify code.

The OU view deserves its own file, and the guest info is actually a
person view and should live with  the other person views.

The profile page of a guest now shows a verification button if the guest
has a passport or national identificaiton number that has not been
verified. Clicking the button shows a dialog, with a confirmation button
which triggers a PATCH request to the backend and reloads the page when
it returns.

Resolves: GREG-101

Code for guest routes moved to their own folder so that we don't need
multiple api calls.
Serializer class for roles has been simplified with methods for
validation of each field and a separate one used in invites without
requiring the person field.

Resolves: GREG-61

Allows search using e-mail and mobile phone, limiting results to 10
first matches

To make handling info about roles and persons easier we split them into
separate objects. The Profile page has now gotten its own api endpoint
where a sponsor has access to all guests instead of only those they are
sponsor for which is used on the sponsor frontpage. This is necessary
since a sponsor may want to give a role to someone they are not
currently sponsor for.