GetManagers returns all the managers registered.

GetIdentityDeserializer returns the IdentityDeserializer for the given chain.

GetLocalMSP returns the local msp (and creates it if it doesn't exist).

GetManagerForChain returns the msp manager for the supplied chain; if no such manager exists, one is created.

XXXSetMSPManager is a stopgap solution to transition from the custom MSP config block parsing to the channelconfig.Resources interface, while preserving the problematic singleton nature of the MSP manager.