RFC: simplifications and suggestions on open/accept limits.

In a discussion about the use of dust limit as an atomic unit on Bitcoin, Christian Decker stated that the dust rules prevent outputs smaller than 546 satoshis. This means transferred value and fees would always be multiples of the dust limit. However, Gert-Jaap argued that his minimum HTLC should be 546, but it doesn't mean that every transferred value must be multiples of that. He believes that the protocol could allow for trustless payments of even 1 satoshi.Gert-Jaap also suggested that since values not representable or enforceable on-chain will still exist, it would be best to keep msatoshis for broader applicability. He added that while he agrees with giving users the freedom to choose their preferred unit of transfer, it also comes at the cost of complexity. Therefore, finding the right configuration options is important, but he does not envision this to be configurable by end-users.