Dataviews: Add real hyperlinks

This adds a real hyperlink in all the <a> tags in the dataviews. That way,
one can open a Stack in a new tab, or bookmark the link.
Dataviews: only execute JS link

Added "return false" to all JS links to prevent default browser behaviour
(following the link). That way the address bar is not changed when simply
clicking a link.
Update h5py to 2.3.1

Building h5py <= 2.3.0 fails with the latest hdf5 (1.8.13).
This was fixed in h5py 2.3.1, see [1].

[1] https://github.com/h5py/h5py/issues/446
Merge pull request #781 from fzadow/new-h5py-version

Update h5py to 2.3.1 in pip-frozen
Merge pull request #766 from fzadow/real-links-in-dataview

Real links in dataviews
Fix wrong default for maximum size of generated files

In commit e8c4ca6c a maximum size for generated files was introduced
(e.g. used in the cropping module). The intendet default was 50MB, but a
byte representation of 51200 was set. This commit changes this to
52428800, which is the correct number of bytes in 50MB.

Thanks Felix von Zadow (@fzadow) for the pointer!
AnalyzeArbor: histograms of cumulative counts alongside the regular ones.
Merge branch 'master' of github.com:acardona/CATMAID
Cropping: fix estimation of total file size of sub-stack

The accumulation of the data read so far was reset for every slice. This was
wrong, because the estimation is checked against the limit for the whole file
(i.e. all slices).

Thanks to Felix von Zadow (@fzadow) for the pointer!
utils.js setup for vim tabulation at 2 spaces
new function SVGUtils.insertXYScatterPlot
AnalyzeArbor: scatterplots for cable vs depth and cable vs inputs.
AnalyzeArbor: fix error in generating scatter plots (too many!)
AnalyzeArbor: fix error in plot of cable vs depth
3D viewer: listen to events for lost and restore context

WebGL context can be lost and suddenly disappear. This is usually due to
a lack of resources. See [1] for some more details. The 3D viewer should
listen to those events and tell the user what is going on. Ideally, it
can also restore the 3D viewer once there is a context available again.
This commit realizes the first part, which at least makes sure CATMAID
doesn't crash anymore when the context is lost.

This is related to issue #774.

[1] https://www.khronos.org/webgl/wiki/HandlingContextLost
3D viewer: remove some accidentally added characters
Neuron dendrogram: fix shortcut typo and order
Annotation search: reset 'select all' checkbox on each page change
Add shortcut to append active skeleton to selection

Create a keyboard shortcut to append the active skeleton to the last
used selection widget. SelectionTable now tracks the last focused
selection widget. Currently this shortcut is bound to 'Y'.

Thanks to Anton Miroschnikow for the original feature request.
Selection widget: fix window not taking focus

Because it does not call addLogic, the selection widget window was not
taking focus. It displayed as focused, but did not remove focus from
other windows and did not trigger focus listeners.