Change the supports column in drug_hoi_evidence from boolean to varchar in ohdsiTest3.psql

[rkboyce]

The reasons for this change are as follows:

• there are null valued supports values
• the drug_hoi_evidence table, when copied into needs a varchar because some DBMS don't support
  'boolean'
• It makes it easier to write WebAPI calls.

[ericaVoss]

Double checked this today and it is still boolean. We can handle this later.