vibc-core clean up - post phase 2

[RnkSngh]

Very slight changes to contracts that can be saved until after phase 2:

• Add packet commitment getters to make it easier for dapps to query packet commitments on chain & make it easier for relayer to find the state of packets (pending contract size)
• get rid of chanOpeninit callback?
• use 2step ownable for dispatcher
• Adding channelid and portid will allow us to map errors to a specific channel/port (pending contract size)