Ignore pattern modification and override changes

[calmh (Jakob Borg)]

Items in the ownCloud client’s ignore list can be marked such that the client is allowed to delete them if they are preventing removal of a directory.

This is probably something we should emulate.

[Zillode]

Could you have a look at https://github.com/Zillode/syncthing/commit/10021c97a66dba283aa558ca08371a57c69448b8 and tell us what’s missing? I cannot reproduce the behavior you describe and everything works as intended.