Annotations: fix basic query generation

The modifications of the queryset generation I added in 006228b were
wrong and did not work as expected. We should start to use some unit
tests for these things. This commit fixes the queryset generation and
makes it more straight forward to understand. It fixes #667.
Review widget: ignore 'auto centering' setting on segment init

When starting reviewing a segment, the 'auto centering' setting should be
ignored. Otherwise one is not able to find the new segment. This commit
implements this and the new segment is centered, regardless of the 'auto
centering' setting.

This fixes #670. Thanks to Ingrid Andrade for reporting this problem.
Review system: add missing review updates on split and join

When skeletons are joined or split, threre is always one skeleton removed or
created, respectively. In these situations all reviews of the treenodes
belonging to the removed or created treenode need to be updated, because the
skeleton ID is part of the review table. The column is there for performance
reasons and has to be kept up-to-date when a tree node moves to a different
skelton.

This fixes #670. Thanks to Loni Brueckmann for reporting this problem.
3D viewer: fix wrong index for compact-json access

In commit ade90b8 I removed the reviewer field from the treenode representation
in the compact-json API. Therefore many indices had to change that are used to
access the response object. One index was forgotten, which is fixed by this
commit.
3D viewer: don't save reviews as node properties

Attaching the review information to each node hits performance significantly.
Therefore, this commit stores the returned review information as property of
each skeleton object. Shading methods can access this field, if they need it.
This also simplifies the delayed loading of the review information, which will
be added soon.

This is related to issue #668.
Implemented group graph widget.
Fix issue destroying OptionDialog instances: they weren't before.
Merge remote-tracking branch 'origin/master' into group-graph

Conflicts:
	django/applications/catmaid/static/widgets/compartment_graph_widget.js
	django/applications/catmaid/static/widgets/graph_plot.js
Group Graph: Fix error with creating Hex colors for coloring nodes.
Group Graph: enable coloring by own or union of reviews.
Fix error in group graph.
Statistics widget: fix typo that prevented display of connector number

Thanks to Javier Valdes Aleman for reporting this bug.
Add migration to ensure consistensy of review table

Due to a bug (that was fixed recently) it could be the case that there
are reviews in the review table that link to a wrong skeleton. The
problem was that a review's skeleton reference was not updated when
skeletons were merged or split. With the help of the migration added in
this commit, the review table is made consistent. That is, all reviews
are checked and if the skeleton they reference is another one that their
treenode references, the review is updated to reference the treenode's
skeleton.
Review widget: simplify test for a valid segment
Review widget: fix respecting followed users on next segment selection

If a checkbox for a user on top of a column is checked, their reviews will be
respected when the next segment is selected. This means if they have reviewed a
segment by a 100 percent, it will be skipped for selecting the next segment for
review. Unfortunately, this did not really work before and this commit fixes it.

Thanks to Javier Valdes Aleman for reporting this bug.
Review widget: add small explanatory tool tip to header checkboxes
Make neuron name visible in title bar again

This is related to issue #672.
Group Graph: fix errors generating group IDs.
Merge branch 'master' of github.com:acardona/CATMAID
Group graph: remove large self-comment.