Various Oracle conversion script fixes

When Western upgraded from Sakai 11.3 to Sakai 20.2, we compiled all the intermediate conversion scripts together and ran them line by line against our DEV / QA databases, and corrected any errors we encountered before going to production. In doing so, we detected a handful of errors (both syntactic and semantic), for example:

• number columns that default to 0 on MySQL, but default to null on Oracle opening the door to NPEs

• BEGIN... END compound statements that execute in MySQL, but act only as a declaration in PL/SQL, and require a following "/" to actually execute.

I will review the differences between the finished script we used to update our Oracle database in production vs the oracle scripts in sakai-reference/documentation/conversions and submit a PR.