update search lucene to v0.6.0 for stable7, requires migration test

Thx a lot @icewind1991 and @Raydiation for doing the initial code review and to @LukasReschke for being the first to confirm a full migration test to me. This still needs one more migration review:
1. set up OC6 with sqlite and upload some files, 
2. click in the search bar to make sure the files have been indexed by search_lucene (wait until the counter has indexed at least a few files).
3. Verify there are indeed duplicate ids: SELECT * FROM oc_lucene_status (I could only reproduce with sqlite)
4. close the browser tab and rename the install directory
5. unpack OC7,
6. replace search lucene with master: cd apps; rm -rf search_lucene; git clone git@github.com:owncloud/search_lucene.git
7. copy old config and move over data dir
8. perform update by navigating to web frontend or running php occ upgrade

Merging will fix https://github.com/owncloud/core/issues/10205