Refs #8163. Add run_number to log list.

Don't add it automatically. Gets represented as double for now.
Refs #8163. Using QVariant to store log values.
Refs #8163. Better variable name.
Refs #8163. Make string logs to be displayed as text.

This is done in general way, so if we'll need to add logs of various
types it will be easy.
Refs #8163. Select Run Number log value by default.
Refs #8163. Remember if user has de-selected the log value.

Plus solved another problem with remembered states not being cleared
before saving new ones. It caused check-box which was once checked by
user to be re-checked every time results tab is opened.
Merge branch 'feature/8163_muon_runnumber_as_log' into develop