Merge pull request #533 from mbrotz/bugfixes

Fix for issue #532.
Refactor gitignore
Replace tab with spaces
Change comments and idea module dirs
Simplify world listing and change to dates in ISO 8601 format. WOO ISO 8601 !
Merge pull request #535 from mkalb/gitGradle

Refactor gitignore and build.gradle
Rename a Dev class to avoid a naming conflict in IntelliJ. This previewer hasn't actually worked for who knows how long anyway (wonder how long ago we deleted "Biomes.png" ..) - but don't want to start a deletion spree or anything
Miniscule fix for missing space in single player ui.