Unify SQL filenames, sort sql.qrc

Unify SQL filenames, sort sql.qrc

Unify SQL filenames, renaming PostgreSQL 'select_messages' to
'select_messagesNewestK', and renaming SQLite 'select_messages' to
'select_messagesRange'.

Sort sql.qrc alphabetically.

This makes it easier to see which functionality is related, e.g. when
making future schema changes.  Sorting improves 'git diff' output.