Fixing some configuration issues with issue validators and container config
Adding logic to start issue numbers from 10001 when no previous issue exists
gitignore cleanup
Making some non-required fields on Issue nullable, fixing event listener config for IssueNumberListener so it runs before create
Fixing logic in IssueRepository::findLastIssueNumberForProject() so that when no issue is found, it returns null
Fixing broken test assertion for IssueFormTypeTest
Adding IssueNumber value object to represent an issue's full number
Adding assertion to ensure objects with __toString() methods work as expected with DomainObjectArrayDecorator