With UN/LOCODE support, storage node may have
`UN-LOCODE` attribute. Policy parser should support
both `Ident` and `Strings` as filter keys to parse
rules such as `FILTER "UN-LOCODE" EQ "RU LED" AS F`.
Signed-off-by: Alex Vanin <alexey@nspcc.ru>
JSON format is rather verbose an inconvenient to be
edited by hand. This commit implements SQL-like
language for representing placement policy.
Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>