support for newer, but backward compatible taxonomy OR better error message

[mtholder]

I just built OTT3.6, which adds some taxa to OTT3.5. I need to remap some taxa to it and then build a new synth tree. It appears that I'll have to:

1. build a synth tree on OTT3.6,
2. deploy the new OTT and the new synth.
3. remap taxa based on OTT3.6
4. build a new synth tree with the newly mapped taxa
5. redeploy that new synth

It'd be nice if we had a flag that indicated that it as OK if the OTT-version and synth tree's OTT-version didn't match.

Even if we don't support that, we should probably reword the last error message when otc-tol-ws crashes because of this mismatch. Now the logged messages (see below) make it look like there are problems with 2 files that are actually fine. The penultimate message is the reason for the crash.

Tree with <synth_id='opentree14.7',taxonomy_version='3.5draft1'> does not match taxonomy version '3.6draft1' (= or modified)
Rejected ""/home/deploy/ws_dir/otc_ws_data/synth_trees/opentree14.7"" due to lack of "/home/deploy/ws_dir/otc_ws_data/synth_trees/opentree14.7/labelled_supertree/labelled_supertree.tre" or lack of "/home/deploy/ws_dir/otc_ws_data/synth_trees/opentree14.7/annotated_supertree/annotations.json" or parsing error.