Improvements to the new Fabric project type

[Leo40Git]

• Mod ID field (since just reusing the mod name is a bad idea)
• Root package field (instead of always using the Maven group ID)
• Have the mod name field actually affect the mod name, rather than using the project name (is this one even intentional?)

[Leo40Git]

• Have the "Repository" field populate contact.sources rather than custom field contact.repo

[Leo40Git]

• Have the "Website" field populate contact.homepage rather than custom field contact.website