Modifies logging of errno errors to resemble com_err's handling of ext2fs errors
Adds handling of capabilities to drop permissions when fssort is executed setuid
Employs capabilities handling

Permissions are raised only for opening a new file system and the capabilities
only allow read access
Configures cmake to install the executable setuid
Refactors Capabilities to be applicable before arguments are parsed and to
reduce number of sys-calls in case of failure