Improve implementation of qvariant typing

...est/kotlin/de/justjanne/libquassel/client/EndToEndTest.kt

.../libquassel/protocol/connection/ClientHeaderSerializer.kt

...ne/libquassel/protocol/connection/CoreHeaderSerializer.kt

.../libquassel/protocol/connection/ProtocolMetaSerializer.kt

...lin/de/justjanne/libquassel/protocol/models/BufferInfo.kt

...ustjanne/libquassel/protocol/models/DccIpDetectionMode.kt

...tjanne/libquassel/protocol/models/DccPortSelectionMode.kt

.../justjanne/libquassel/protocol/models/HandshakeMessage.kt

...kotlin/de/justjanne/libquassel/protocol/models/Message.kt

...tjanne/libquassel/protocol/models/NetworkLayerProtocol.kt

...in/de/justjanne/libquassel/protocol/models/QStringList.kt

...ustjanne/libquassel/protocol/models/SignalProxyMessage.kt

...otlin/de/justjanne/libquassel/protocol/models/TimeSpec.kt

...tjanne/libquassel/protocol/models/flags/BufferActivity.kt

.../justjanne/libquassel/protocol/models/flags/BufferType.kt

...justjanne/libquassel/protocol/models/flags/MessageFlag.kt

...justjanne/libquassel/protocol/models/flags/MessageType.kt

...n/de/justjanne/libquassel/protocol/models/ids/BufferId.kt

...de/justjanne/libquassel/protocol/models/ids/IdentityId.kt

...tlin/de/justjanne/libquassel/protocol/models/ids/MsgId.kt