label work; adds preliminary _j2sclasslist.txt

label work; adds preliminary _j2sclasslist.txt

- use get class list link on test page to save list
- run buildcore.xml, which creates j2s/core/core_jalview.z.js (3.8 Mb)
- open jalview_bin_JalviewJS_core.html (if it is not in site/ copy it
from site-resources -- the transpiler should do this, but not unless you
change the code)

On my machine, Chrome loads and displays the reference JAXB file in
under five seconds.

The mechanism of dynamic loading of core files (not just preloading,
like this) might not be implemented yet in SwingJS.

TODO: menus are not automatically closing on the 300-ms timer anymore. Something I did when reconfiguring CSS for menu items. Will check.