[performance] Consistency checks take too long when creating backup on large db: by default, consistency check will now only test if a document's data can be read. Extended checks, which will traverse every document to test for DOM errors, can be enabled via a parameter. To reduce IO, documents are now accessed in the order they are stored in dom.dbx (makes the checks 3 times faster).
Merge pull request #235 from wolfgangmm/develop

Fix performance of consistency check and export
[performance] Removing collection with many docs/subcollections results in huge recovery log, because the list of freed collection/doc IDs is updated continuously and written to disk. Solution: keep list of unused collection/doc IDs in memory only to reduce IO. The downside is that those lists will get lost if the db is restarted, so some spare IDs might not be reused. This trade off seems acceptable though. Having some gaps in the assigned IDs is ok.
Merge pull request #236 from wolfgangmm/develop

[performance] Removing collection with many docs/subcollections results ...