Improved functionality for synchronization filters

[Nicklas Nordborg]

Synchronization filters in item lists are very useful, but one drawback is that items must match all filters in order to get included in the list.

It would be nice if some kind of "OR-like" functionality could be implemented. For example: Items should match filters 1, 2 and 3 or filters 4 and 5. This would help a lot in a lot of situations which currently requires 3 item lists (one list with filters 1, 2 and 3; a second list with filters 4 and 5; and third list that is combining the first two).

If possible, it would also be nice to have a "NOT-like" functionality. For example: In addition to the above, always exclude items matching filter 6.

[Nicklas Nordborg]

In 7881:

References #2232: Improved functionality for synchronization filters

Implemented a "Filter group" functionality. A synchronization filter must always belong to a "filter group" (default is A+). The name of a filter group is always one character A-Z followed by + or -.

Each group may have multiple filters and an item must match all filters in the group to be selected by that group.

Filter groups are merged in alphabetical order (A+, A-, B+, B-, ..., Z+, Z-). Items in + groups are included in the list and items in - groups are excluded from the list.

Note that if an item matces multiple groups, the last group "wins". For example, if an item is included by A+, it may be removed by B- and then included again by C+.

[Nicklas Nordborg]

In 7882:

References #2232: Improved functionality for synchronization filters

Some minor display changes.

[Nicklas Nordborg]

In 7884:

References #2232: Improved functionality for synchronization filters

Added a "New filter" button for every filter groups in the list to make it easier to add filters to the same group.

[Nicklas Nordborg]

In 7901:

References #2232: Improved functionality for synchronization filters

Updated the documentation with information about this feature.