analysis_web_data column db_type should be an enum rather than a set

we need one separate entry for each db_type

misc-scripts/production_database/sql/patches/patch_70_71a.sql

+-- Patching in support for comments on web data
+
+ALTER TABLE analysis_web_data
+MODIFY COLUMN db_type enum('cdna','core','funcgen','otherfeatures','rnaseq','vega','presite','sangervega') NOT NULL DEFAULT 'core';