Add tables for module inputs/outputs #45
Description
Each kind of module input and output has some associated data. Currently, only some of the LN input/output data is exposed in an inelegant fashion by adding it to the main transaction_{input_output} tables.
Ideally the transaction_{input,output} tables would only contain the input/output kind, module instance id and amount. All the module-specific data should live in module-specific tables, only referencing the main input/output tables. E.g. there could be a mint_outputs table that contains blind nonces.