Motivation:
* Path attribute should be null, not empty String, if it's passed as "Path=".
* Only extract attribute value when the name is recognized.
* Only extract Expires attribute value String if MaxAge is undefined as it has precedence.
Modification:
Modify ClientCookieDecoder.
Add "testIgnoreEmptyPath" test in ClientCookieDecoderTest.
Result:
More idyomatic Path behavior (like Domain).
Minor performance improvement in some corner cases.