web/.htaccess, web/username_prefix.php: username-based prefix subpaths: support query strings in addition to paths

web/index.php: removed no longer needed redirection of username-based prefix subpaths, which is now handled by web/.htaccess

web/.htaccess: handle username-based prefix subpaths (of the form "subpath@url?") for all paths rather than just for the root (which were handled by index.php)

added web/username_prefix.php, for use with username-based prefix redirects

web/index.php: subpath@host? redirects: also support multiple @ and nested . in prefix: a@b.c@host? -> host?b.c.a

web/index.php: support prefix redirect of the form subpath@host? , which is better than subpath.host because case is preserved and special chars allowed. (must require trailing ? for redirect, to avoid needing login to view the page itself.)

bugfix: web/index.php: full directory index: appending query string: need to use $_SERVER["QUERY_STRING"], not $_SERVER["HTTP_AUTHORIZATION"] for this

schemas/public_.sql: sync_*(): renamed to *_modify() to facilitate finding these functions when modifying the corresponding view (using the new naming convention for a view's on-modify function)

bugfix: inputs/.TNRS/schema.sql: MatchedTaxon_modify(): updated to include taxon_scrub derived fields

bugfix: schemas/util.sql: mk_drop_from_create(): need to match first rather than last CREATE