Rename IsPartner to PartnerMask

Add documentation for IsPartner

Add Partner properties to Npc entity

Pass OwnerId from DropPacket to GroundItem

chore: remove unnecessary target framework netstandard2.1 for Core tests

fix(core): make managed nostale client constructor public

feat(core): add support for raw packet responder from AddPacketResponder

chore: bump versions

tests: adapt Game tests to new features

fix(packets): check if header to packet contains the key to look for

tests: add new fields to su packet

feat(core): split raw client and managed client as well as packet handlers

Resolves #65

fix(core): do not try to create stateful instance in case the entity is already present

fix(core): make stateful repository return the correct type

feat(core): add possibility to add items to stateful repository manually

chore: make README.md be copied to root of package

chore: include readme and license in package

chore: move repository url and license to Directory.Build.props

fix(packets): put correct attribute to pst packet effects

fix(packets): deserialize upgrade rare sub packet "-1"