Added test for HEAD request with rev query parameter, check DELETE requests for conflicts when using rev parameter.
Return 409 Conflict HTTP status for PUT requests if the rev parameter is not the latest revision.
Add If-Match header for DELETE method.
Add tests for If-Match headerd for DELETE method.
Test DELETE method with if-match header.
Test GET and HEAD requests with if-none-match header.
Change the branch for multiversion module in .travis.yml.
Implemented the rev query parameter for PUT requests.
Use the 8.x-1.x branch for multiversion module.
Merge pull request #9 from dickolsson/2352527-404-missing-rev

Issue #2352527 by jeqq: Fixed Implement the rev query paramater for HEAD, GET, PUT and DELETE requests.
Initial resource to return all entity types in the system.
Add comment to get method.
Return workspaces names in GET call.
Add test for _all_dbs call.
Sort workspace arrays.
Rename files.
Adjust comments. Remove not needed use classes.
Merge pull request #10 from ygerasimov/2361449-all-dbs

Issue #2361449 by ygerasimov: Implement /_all_dbs.
Test with Multiversion branch 2351209-transaction-manager
Fixed serialization tests