Have adjustable default values for user profiles
Use a custom template view for CATMAID's homepage
Add visibility setting to user profile for each tool category

There are different use cases for CATMAID and not everyone needs every
tool. In fact, additional tool buttons might even confuse users.
This commit introduces therefore five new user profile settings: the
visibility of the text label, tagging, cropping, segmentation and and
tracing tool.

By default these settings are all set to hide all tool options. These
default values can be controlled in CATMAID's settings file so that the
default tool set can be set for each instance. Independent of that,
tools can be shown/hidden for each user from within the admin area.
Merge branch 'modular-tool-display'