Fixes Forge Class trying to create UNSIGNED fields in Postgresql

[gustavojm]

UNSIGNED is not a supported datatype in Postgre
overridden method _processColumn()

Tries to solve #719 .
Take it with a grain of salt as it's my first PR ever!

[jim-parry]

1. Your private application code does not belong in the CI4 repository
2. Your private database settings do not belong either
3. Comments (including commit messages) should be in English
4. contributions should be GPG-signed
5. You have added a composer dependency that doesn't work with travis-ci, by the look of it
6. Affecting 214 files suggests that you might be inadvertently including more than you planned in your PR

Good try, but work needs to be done!
Apart from fixing the above, you will find it easier to create a feature branch for just the changes pertaining to your fixes, rather than trying to merge your entire develop branch.

[gustavojm]

Jim, sorry for what happened, I initally forked a clean copy of CI4, made the changes to fix the issue, created the PR and I thought that it was it...
Then I merged another local repo I was working on previously but didn't expect it to end up in the PR.

[jim-parry]

Oops. That's what happens when you don't do fixes in a feature branch!