Query application contract for metadata

[guidanoli]

The IApplication interface provides two view functions that could be called by the DaveConsensus contract to query key metadata:

• getTemplateHash: the initial machine state hash
  • Also known as "template" hash
• getDataAvailability: the data availability solution used by the application
  • The only currently supported option is the on-chain InputBox contract

This would remove the need to pass this information as construction arguments to the DaveConsensus contract, and require the application developer to pass the correct information during construction of the Application contract.