Revert "merge with 2.0"

This reverts commit 1a2ede3001feca08d1ffd37387b4e4deba43a79a.
code refactor
Merge branch 'feature/virtual_create_cluster_session' into feature/named_parameters
code refactor
Merge branch 'feature/virtual_create_cluster_session' into feature/named_parameters

Conflicts:
	Cassandra.Data/CqlConnection.cs
add more comments
Merge branch 'feature/virtual_create_cluster_session' into feature/named_parameters

Conflicts:
	Cassandra.Data/CqlConnection.cs
make prepated statement cacheable
Merge branch 'feature/named_parameters'

Conflicts:
	Cassandra/Properties/AssemblyInfo.cs