Add an index verifying command (index-check)
mark some duplicated logic.
update a tiny bit of naming consistency.
Make BlockStore iterable.
Make BlockStore no longer visitable.
Tidy up notes.
drop unused IONotReadyException.
Simplify tests for IndexVolumeMain
clarify IndexSearchMainTest
create IndexStore
Use IndexStore in IndexSearch.
make an in memory index store for testing.
specialise tests of IndexSearchMain and IndexStoreFileSystem
make IndexSearchMain stop using System.err
make CriticalListMain stop using System.out and System.err
make LocalCandidateListMain stop using System.out and System.err
drop unused parts of FileSystem and related classes.
drop an almost unused method in FileSystem, correcting tests that used
it.
drop another unused part of FileSystem