Introduce CDTMutableDocumentRevision

Created CDTMutableDocumentRevision Class
Modified CDTDatastore to add create, update and delete APIs that use Revisions.
Added basic tests for new APIs
Modified CDTDocumentRevision to add mutablecopy method

Deprecated CDTDocumentBody
Deprecated CDTDocumentRevision method documentAsDictionary

Note: CDTMutableDocumentRevision does not handle attachments yet, this functionality will be added in a later PR
Did you mean something like this:


      NSMutableDictionary *mutableCopy = [_td_rev.body.properties mutableCopy];
        
        NSPredicate *_prefixPredicate = [NSPredicate predicateWithFormat:@" self BEGINSWITH '_'"];
        
        NSArray * keysToRemove = [[_td_rev.body.properties allKeys]
                                  filteredArrayUsingPredicate: _prefixPredicate];
        
        [mutableCopy removeObjectsForKeys:keysToRemove];
        _body = [NSDictionary dictionaryWithDictionary:mutableCopy];
 

I could't find ``` -filteredArrayUsingPredicate``` or similar method on the ``NSDictionary``` from ```_td_rev.body.properties ```