Include description of error codes

broader requirement/initiative to improve documentation of our error codes across all products.
It looks like some inconsistencies across our CBL products
  * CBL-C. https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-c/C/html/group__errors.html#gad43e348ca76e9a8fe7c10ec916bf0528. 

• • Looks good
• .NET https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-net/api/Couchbase.Lite.CouchbaseLiteError.html. 
  • Looks good
• ObjC. https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-objc/Constants.html
  • Description is missing. I realize that CBLErrors.h header is  included in the downloaded package. Is that what developers must refer to?
• Swift.  Nothing in API docs.  (looks like the ObjC constants get bridged up).  How do swift developers find those in https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-swift/. I realize that CBLErrors.h header is included in the downloaded package. Is that what developers must refer to?
• Android. https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-android/com/couchbase/lite/CBLError.Code.html.
  • Description is missing
• Java. https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-java/com/couchbase/lite/CBLError.Code.html
  • Description is missing

Task 

Android, Java, iOS (ObjC) : Update error code description to be consistent with what .NET has (https://docs.couchbase.com/mobile/3.0.0-beta02/couchbase-lite-net/api/Couchbase.Lite.CouchbaseLiteError.html. )