Show OTT taxon id next to other source taxonomies.

Fixes #442.
Label OTTid 'Reference taxonomy'; smart EOL search

Don't bother offering EOL search for non-taxon nodes.
Safer URLs for subtree downloads and unnamed nodes.

This also fixes a previously unreported bug where moving to a node in
the tree viewer would work, but starting fresh from its URL would fail
due to trailing "...". This is now stripped in `makeSafeForWeb2pyURL()`.
Merge pull request #459 from OpenTreeOfLife/show-ottid-in-viewer

Show OTT taxon id next to other source taxonomies.
Tested on aster.opentreeoflife.org.