make drbotzo_modules.module a primary key so that we can use INSERT OR REPLACE INTO

WARNING! if you have an existing drbotzo_modules, you MUST RECREATE IT
WITH THE PRIMARY KEY. things will be wonky without it.

easiest way is to (by hand) create drbotzo_modules_temp as shown in the code,
INSERT INTO drbotzo_modules_temp SELECT * FROM drbotzo_modules, DROP the old
table, and ALTER TABLE RENAME TO the new one.

again, if you don't do this, newer modules will do all sorts of crazy
things, namely trying to create tables that already exist (because they have
multiple, differing values in drbotzo_modules)

dr.botzo.py

@@ -72,7 +72,7 @@ try:
             # need to create the drbotzo_modules table
             query = """
                 CREATE TABLE drbotzo_modules (
-                    module TEXT,
+                    module TEXT PRIMARY KEY,
                     version INTEGER
                 )
             """