[#12] Add READONLY to all tables

READONLY was previously implied by default in Octo due to the use of START and END keywords, among others. This makes it explicit in order for us to ensure that there is no way that VistA table's underlying global data could be killed accidentally.

Sample DD:

DROP TABLE IF EXISTS `TITLE`;
CREATE TABLE `TITLE`(
 `TITLE_ID` NUMERIC PRIMARY KEY START 0 END "'(keys(""TITLE_ID""))!(keys(""TITLE_ID"")="""")",
 `NAME` CHARACTER(30) NOT NULL GLOBAL "^DIC(3.1,keys(""TITLE_ID""),0)" PIECE 1
)
GLOBAL "^DIC(3.1,keys(""TITLE_ID""))" READONLY
DELIM "^";