Several bug fixes and extensions made

- Fixed a bug that let directories still resist online, even if their
relating package were deleted
- Changed way of saving the SQL-data in the project
- Fixed a bug that let clients still run software when cancelling the
package download even if "MustUpdate" was set to "true"
- Fixed a bug that hided the loading panel in ProjectEditDialog when
performing an async operation
- Extended NewProjectDialog
- Extended ProjectEditDialog
- Hardcoded string literals in PackageAddDialog
- Improved some code
- more...