Add method to get ordered nucleotides.

get_ordered_nts is a way to extract all ordered nucleotides for the best chains
and models for a given pdb. This does not handle the error case of no entries in
pdb_unit_ordering for a given pdb.
Update controller for 2D diagrams
Add routing for 2D diagrams
Add method to get ordered nts with new style ids.
Add view for 2D diagrams
Update css for 2D diagrams
Add js for drawing 2D
Mark cWW toggle with cWW family.
Close 2d container div.
Prefix css rules with pdb-2d-view class.

I use pdb-2d-view to indicate we are looking at the 2d view page for each pdb.
By prefixing all rules with this we avoid conflicts with other pages.
Convert IDs and add basic interactions.

Turns out that | is used in some types of css selectors. See:
http://www.w3.org/TR/CSS2/selector.html#attribute-selectors
This conflicts with using | as a separator in our new style ids. In order to
deal with that I modified the getID and getNT methods for nucleotides and
interactions. These now convert the | to _. In addition I activated the basic
interaction controls.
When hovering over an interaction show nucleotides

This will show the nucleotides when hovering. It uses the color of the
interaction to color the letter to make it clear.
Highlight nucleotides on mouseover.

A nucleotide will be highlighted by having its sequence displayed, and any
interactions leading involving it will be highlighted.
Add jmol interactions.

This can now show 3D structures using jmol and a selection region.
Add 2D link to all tabs
Produce empty array when no ordered NTS exist.

We should produce an empty array when we can't find the ordered nucleotides,
otherwise this causes an error.
Add basic warning when no 2D can be drawn.

The warning will only be displayed if there are no ordered nucleotides. In this
case we can't even draw a backbone so we just put up a warning instead.
Fail nicely when no interactions are known.

In this case we can still draw a backbone so we do that, even though there are
no interactions.
Trigger rendering.

Last commit disabled actually drawing the diagram. This fixes that.
More informative message when no nts found.