Changed names related to all namespaces modal.

It's now referenced as search namespace. This will match the upcoming
changes which we'll only show the non-loaded namespaces by default.
Refactored escaping/unescaping namespaces and vars.

In the process of simplifying the namespaces and vars lists.
Refactored some tests to be more clear.
Modified nsList and varList.

From now they are regular lists. The separation to name and url is done
in index.html using the newly created 'escape' filter.
Toggle loaded namespaces display (in search namespaces).

Also changed the default selected namespace behavior. Instead of
selecting the first one, there is no default selection. You get an alert
if no namespace is selected.
Merge branch 'feature/toggle-list-loaded-nses' into develop
Fixed confusing terminology (require -> load)

Although the action of loading of namespace is called 'require' it
creates confusing terminology. Because of that I renamed some reference
from 'require' to 'load'.