sql: Add blacklist, whitelist for group

Add list of blacklisted and whitelisted servers to group. The string is
supposed to be canonical (lexical sorted, space separated) as produced
by keywordset_get(), so that groups with equal sets can be found by sql
string compare.

mysql/create_tables.sql

@@ -4,6 +4,8 @@ CREATE TABLE IF NOT EXISTS mxq_group (
    group_status   INT1 UNSIGNED NOT NULL DEFAULT 0,
    group_flags    INT8 UNSIGNED NOT NULL DEFAULT 0,
    group_priority INT2 UNSIGNED NOT NULL DEFAULT 127,
+   group_blacklist VARCHAR(1000) NOT NULL DEFAULT '',
+   group_whitelist VARCHAR(1000) NOT NULL DEFAULT '',
 
    user_uid        INT4 UNSIGNED   NOT NULL,
    user_name       VARCHAR(256)    NOT NULL,