Move general project access URL into own statement

This is part of an effort to make the URL configuration and the control
package more readable and maintainable. I double checked, that all
catmaid.control imports removed, where not in use in other places.

This commit relates to issue #570.
Remove segmentation slice info method from stack module

This method isn't needed in it's current form. Most parts of the related
code was removed recently. The segmentation code is currently reworked
in a separate branch.
Move general stack access URLs into own statement

This is part of an effort to make the URL configuration and the control
package more readable and maintainable. I double checked, that all
catmaid.control imports removed, where not in use in other places.

This commit relates to issue #570.
Remove useranalytics namespace import from catmaid.control package

Besides removing the useranalytics namespace import from the
catmaid.control package, this commit also adds the authentication prefix
to the URL configuration where required. This is part of an effort to
make the URL configuration and the control package more readable and
maintainable.

I double checked, that all catmaid.control imports removed, where not in
use in other places.

This commit relates to issue #570.