Adding support for DataContract serializers

[MichaCo]

• [x] merge the pull request #200 from @rebulanyum
• [x] fix implementation to use base objects (CacheSerializer and SerializerCacheItem properly) There is a lot of important logic in one place, especially regarding expiration, which shouldn't be copied (was wrong anyways in the initial PR)
• [x] fix missing ctors leading to config not actually passed through and/or exceptions during usage
• [x] add missing unit tests for actually using the new serializers
• [x] code/style cleanup
• [x] produce new nuget