web/.htaccess: username-based prefix subpaths: allow explicitly disabling in a RewriteRule to handle special cases

web/.htaccess: auto-detect dotpath: removed handling of no longer used @ prefix (used to be used by username-based prefix subpaths)

bugfix: web/index.php: directory index: use QUERY_STRING, not HTTP_AUTHORIZATION (HTTP_AUTHORIZATION was probably left over from a previous attempt to provide username-based prefix subpaths)

fix: schemas/public_.sql: analytical_stem_view: vegpath.org links: use ; instead of : between link and definition, because it makes more grammatical sense

schemas/public_.sql: analytical_stem_view: vegpath.org links: removed no longer needed // suffix

web/.htaccess, username_prefix.php: username-based prefix subpaths: don't require the // at the end , to avoid clutter. IMPORTANT: in order to access the home page after visiting a URL with a username, you must now append "." to the host ("vegpath.org.") (other pages are not affected by this problem). since vegpath.org is a URL shortener, this is a worthwhile tradeoff to avoid needing the // suffixes everywhere.

bugfix: web/.htaccess: subdomains: each path element must be non-empty, to avoid matching a trailing . incorrectly

web/.htaccess: username-based prefix subpaths: updated documentation to use leading // instead of trailing ? or ?@

web/username_prefix.php: $_SERVER["PHP_AUTH_USER"] test: factored $_SERVER["SCRIPT_URL"] out of both branches of if statement

web/username_prefix.php: don't remove @ from query string because that is no longer a special character