Removed import that made the thing not compile

It is also not used, so probably the import organizer had a bad day
Implemented SFTP properties configuration via properties dialog for IntelliJ IDEA
added code to keep preferences window open if credentials are not correct
Merge pull request #18 from caiusb/import-fix

Removed import that made the thing not compile
Merge pull request #19 from altern/sftpPropertiesDialogImpl2

Sftp properties dialog implementation