.gitignore : simplify + ignore private
Revert ".gitignore : simplify + ignore private"

This reverts commit 0e5e58a1f87dd6f2feea6cc1366c681129b55358.
gitignore: add explicit list of private files to ignore
gitignore: ignore directory instead of files
Merge pull request #141 from davidB/wip_scenecomposer

.gitignore : simplify + ignore private