Implements mount iso service plugin for dolphin

Implements mount iso service plugin for dolphin

The mountiso plugin adds a contextual menu entry for .iso files to either mount or unmount the file as a loopback device depending on the mount state. This plugin uses UDisks2 DBus API to either mount or unmount the iso file. It also uses Solid to check if an iso file is already mounted.

FEATURE: 175051

Todo:

• use solid to query the loopback device associated with an iso file instead of using losetup
• use UDisks2 DBus api instead of udisksctl to mount and unmount iso file
• documentation using doxygen comments
• describe the mountiso plugin in org.kde.dolphin-plugins.metainfo.xml in english en french

Remaining Questions:

• Should I change the implementation to use the kde Solid framework instead of udisksctl before merging (or maybe fuseiso)?
  • Use Solid instead of losetup
  • Use DBus instead of udisksctl
• Should we enable this plugin by default or not (and how to do this)?
  • enabled by default
• Should we update the project description to mention this plugin?
  • Yes
• Is it necessary to add documentation or maybe a description of the plugin?
  • document code using doxygen
• Is any of the feature used (solid, dbus) non portable?