Refactor serialization of SessionItem (less generic, more explicit)

Serialization means writing and reading of BornAgain project files.

The generic approach makes it very difficult to implement backward compatibility. If e.g. a property name was misspelled ("heigt"), this can't be corrected. Therefore a serialization should be implemented where each data element is expicitly stored/loaded and can be corrected/enhanced/removed/added more easily.

Also the current file versioning is quite limited (only good for whole file OK/NOK, it can't be used for compatibility).

After first discussions, we decided to take a closer look at the boost serialization library.

Another discussion outcome was to go for a single project file solution (either completely created by boost or as a (zip?) archive) instead of a multi-file project stored in a folder structure. This seems more convenient for the users and reduces errors when moving or exchanging files.

Note:
Regarding the design of how to serialize, read also the discussion in !573 (merged): !573 (comment 170494)

This has to be done for

  • Material items
  • Sample items
  • Instrument items
  • Job items
  • Real data items
Edited by Mikhail Svechnikov