Always decode Blob objects from Database::addQuotes

Always decode Blob objects from Database::addQuotes

The current API for Database::encodeBlob/Database::addQuotes requires
the code that is outputting binary data to have a database handle, so
that it may call Database::encodeBlob to get either a plain string or
a Blob object back. All database implementations other than MySQL
return a Blob object from Database::encodeBlob.

This is a rather inconvenient API, it tightly couples the creation of
binary data with the Database object unnecessarily.  If all database
objects accept a Blob via Database::addQuotes then code can simply
wrap its arguments in Blob and know that any database it ends up at
will be properly handled.

This patch changes the default implementation of Database::addQuotes
to recognize a Blob object was passed in, and use Blob::fetch to turn
it back into a string.  Database implementations other than MySQL all
handle this Blob object already.  The postgresql implementation had
to be adjusted slightly. Now when it sees a Blob object that it did
not create it will encode that appropriately.

Bug: 72367
Change-Id: I12fb4bd339be19137fffba2e47a70741382f6a8c