Make database install/upgrade provider aware

Ground work for installing and upgrading database schema based upon DB provider (MySQL, PostgresSQL, SQL Server, etc.)

Cleaned up legacy cruft, refactored, commented and made simpler for to support additional database providers.

core/database/scripts/mysql/db_00021.sql

@@ -0,0 +1,27 @@
+/* community edition */
+
+-- content likes/feedback
+DROP TABLE IF EXISTS `vote`;
+
+CREATE TABLE IF NOT EXISTS `vote` (
+    `id` INT UNSIGNED NOT NULL AUTO_INCREMENT,
+    `refid` CHAR(16) NOT NULL COLLATE utf8_bin,
+    `orgid` CHAR(16) NOT NULL COLLATE utf8_bin,
+    `documentid` CHAR(16) NOT NULL COLLATE utf8_bin,
+    `voter` CHAR(16) NOT NULL DEFAULT '' COLLATE utf8_bin,
+    `vote` INT NOT NULL DEFAULT 0,
+    `created` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    `revised` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE INDEX `idx_vote_id` (`id` ASC),
+    INDEX `idx_vote_refid` (`refid` ASC),
+    INDEX `idx_vote_documentid` (`documentid` ASC),
+    INDEX `idx_vote_orgid` (`orgid` ASC))
+ DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci
+ ENGINE = InnoDB;
+
+CREATE INDEX idx_vote_1 ON vote(orgid,documentid);
+
+-- liking
+ALTER TABLE label ADD COLUMN `likes` VARCHAR(1000) NOT NULL DEFAULT '' AFTER `type`;
+
+-- deprecations