Remove CSS files for Internet Explorer 5, 6 and 7

Currently we don't support Internet Explorer at all and some features and
libraries we use are not supported in IE 5, 6 or 7. For instance, Array's map,
reduce, filter, etc. functions are introduced in IE 9. Libraries like Cytoscape
and parts of CATMAID use the canvas element. Support for it was introduced in IE
9 as well. The 3D viewer uses WebGL, which was introduced in IE 11. Therefore,
there is certainly no need for CSS files that improve support for IE 5, 6 and 7.
Display warning message for unsupported browsers

This adds Modernizr to check browser features and conditionally display
a warning message directing users to use a modern version of Firefox or
Chrome. The specific features checked are:

- opacity
- canvas
- SVG
- JSON
- WebGL

The Modernizr lib was generated with only these features selected, along
with class insertion with 'mod-' as the class prefix. The es5-strictmode
feature, though import to CATMAID, was not used because it wrongly flags
some strictmode-compliant browsers in Modernizr 2.8.3. Other ES5 feature
checks are scheduled to be added in Modernizr 3.

The warning message modally locks out the interface for unsupported
browsers. Browsers supporting all required features except WebGL (IE9,
IE10) are given the option of dismissing the message, since most
browsing and tracing functionality is present. IE11 is fully compliant
and does not display a warning.

Tested on IE6 and IE7 on WinXP, IE8 through IE11 on Win7, current Chrome
and Firefox on Ubuntu 14.04 and OSX 10.9, and Safari 7.0.6 on OSX 10.9.

Closes acardona/CATMAID#557.
Doc: fix typo breaking Celery doc link (minor)
Fix configuration for default Celery broker URL

Add `django` to recognized protocols, since the configuration creation
was rewriting `BROKER_URL` in `settings.py` to `django:/`, which caused
Celery to fall back to amqp and broke the default Kombu configuration.
Export widget: improve UI messages

- Fix missing path string substitution in error message when treenode
  archive directory is not writable
- Fix confusing verb tense for message indicating export is in process
Doc: update administration section to reflect current update procedure
Doc: link to administration section from TOC on front page
Doc: add section about SSL setup to administration setup
Grid layer: set and update SVG size properly

The SVG has to be as big as the stack's view.
Remove CSS extraction from stack and overview map

Refactor the overview map to defer to CSS to set the map container size
and compute overview scale from the computed style instead of parsing
CSS rules. Remove unused CSS extraction from the stack view. Since these
were the only dependents on rule order in `stack.css`, remove rule order
warning comments.

Progress towards removing `getPropertyFromCssRules`.
Remove CSS extraction from slider and cropping

Refactor slider widget to not depend on extracted CSS properties. The
slider handle is now positioned as a percentage of the slider, instead
of in absolute pixels. Slider and handle margins are now controlled by
CSS rather than through JS styling. Non-breaking spaces used as
positioning were removed from slider labels accordingly. CSS extraction
was also removed from sliders in the cropping tool. Since these were the
only dependents on rule order in `slider.css`, rule order warning
comments were removed.

Progress towards removing `getPropertyFromCssRules`.
Tools: remove CSS rule extraction

Remove `getPropertyFromCssRules` and helper function `getCssRules`
because they create brittle dependence on the inclusion order and rule
order of CSS files.
Fix dash key zoom out on Firefox

Since Firefox 15 the dash key (between '0' and '=') has emitted key code
173, rather than 109, which is now only used for the numpad minus key.
(Chrome emits 189 for the dask key.) This change supports this key for
zooming out in the navigator and tracing tool.
3D viewer: create floor as sub-divided plane instead of lines

As it turns out, rendering quads (and triangles) is much faster than rendering
lines. This improves the performance of the 3D viewer quite a bit.
Connectivity widget: remove TableTools

Replace the TableTools DataTables extension with a simple click handler
to export connectivity tables as CSV. Remove the TableTools library.

Revert the majority of fc6ad191e4c46bc7ba43d1c6642fae5e2a4fc1c0
Connectivity widget: use selector for checkboxes

Use a selector to select all checkboxes instead of fixed table and row
child indices. Thresholding partners rearranges the order of table
children, which was breaking the select all checkbox.

Closes acardona/CATMAID#748.
Review widget: fix minor syntax issues
Review widget: don't pass key event if not needed

When a review key (i.e. Q, W or E) is pressed, the tracing tool passed the key
event to to the review widget. This isn't actually needed and complicates
things. This commit removes this parameter from the respective functions and
replaces one use with a dedicated argument.
Review widget: queue selection of next segment after pending requests

The selection of the next segment depends on client side information about the
review state of all nodes of all segments. To select the next segment based on
the latest information, the selection is now queued after currently pending
requests. This makes sure all single node review requests have been handled
before.

This is related to issue #743. Though it isn't clear yet if this was the only
problem that could lead to this behavior.
Review widget: move comment and remove unneeded user name override

By default, the anonymous user (i.e. when no-one is logged in) has ID -1. Back
when the review system didn't support multiple users, -1 as a user ID was also
used to mark a treenode as not reviewed. This has changed and is not done
anymore, because there is now a separate review table containing only actual
reviews. Therefore, we don't need this name override for non-reviewed treenode
entries anymore. Besides this, the name also had a typo in it.