JAL-3065

Change in all repo documentation advising launching Jalview with the
-Djava.ext.dirs=LIB
option to now use
-classpath="LIB/*:..."
instead. Using the -Djava.ext.dirs= option masks the JRE's own ext dir
which contains the sunjce packages.  This manifests as cipher problems
when accessing https resources (in particular https://www.ebi.ac.uk/...
when searching for PDB structures, activated when choosing Sequence->"3D
Structure Data...")