Changed the number of days before student affs are removed.

Made the code slightly more readable while at it.
Changed adding group members to include indirect members.

Previously, only direct members were added for groups, and we would let any
parent group be included if it had the correct AD spread. Now, we include the
indirect members if the parent group does not have an AD spread, by flatten the
targeted group.

Since I'm bad at explaining, how about a figure? :)

Example on a situation in Cerebrum::

    +-------------------------+
    | GroupA (with AD-spread) |
    +-------------------------+
         |               |
    +---------+ +----------------------------+
    | MemberA | | GroupB (without AD-spread) |
    +---------+ +----------------------------+
                         |
                    +---------+
                    | MemberB |
                    +---------+

where GroupA, MemberA and MemberB is supposed to be in AD (have the correct AD
spreads), while GroupB should not be in AD.

In the previous AD sync, this would in AD become::

    +-------------------------+
    | GroupA (with AD-spread) |
    +-------------------------+
         |
    +---------+
    | MemberA |
    +---------+

While with this commit, the structure in AD would look like::

    +-------------------------+
    | GroupA (with AD-spread) |
    +-------------------------+
         |           |
    +---------+ +---------+
    | MemberA | | MemberB |
    +---------+ +---------+

I.e. the group is flattened in this situation. Note, however, that if GroupB had
the correct AD-spread, AD would have the same situation as in Cerebrum, which is
the same behaviour both in the old and the new AD sync.
cereconf'ed the grace period for deleting student affs.
Added support for grace period before removing affs.

This is as requested by UiA. It depends on a cereconf variable,
FS_STUDENT_REMOVE_AFF_GRACE_DAYS, which must be defined (already commited to
UiA's cereconf).
CRB-383: Bugfix, copy-paste-error.
Merge pull request #51 in CRB/cerebrum from CRB-383-project-create-failing to master

* commit 'ce47729dfbe26d76cc23c34487e7347374cb7613':
  CRB-383: Bugfix, copy-paste-error.
Merge pull request #16 in CRB/cerebrum from CRB-344-uio-redusere-grace-perioden-for-studentar to master

* commit '5fd52798b54fe056b1f64007b6759127e6330db4':
  cereconf'ed the grace period for deleting student affs.
  Changed the number of days before student affs are removed.
Merge pull request #38 in CRB/cerebrum from CRB-321-uia-student-aff-rem-grace to master

* commit 'c011bc3358f8bda7493c81d7906a1d40f81dc2b6':
  Added support for grace period before removing affs.
Merge pull request #36 in CRB/cerebrum from CRB-331-indirect-members to master

* commit '4b6cb6266eddadb846c9d050effbae13c01ad718':
  Changed adding group members to include indirect members.