Fixes for SilverStripe 4.5

[gordonbanderson]

hi,

There are 4 commits in this PR. In order they are

1. Import sweep
2. Fix a complaint about a missing method re multiple image uploading. Note that I have not implemented this, I merely wished to get the module working.
3. Fix a method signature to be consistent
4. SQL fix for Postgresql

Please note that I have not tested part 4) with MySQL. Continuous integration is good, but I realize in this instance it would be tricky to implement unit tests (I have had many fights with php-vcr over the years)

Cheers

Gordon