RFC: simplifications and suggestions on open/accept limits.

In an email exchange between Rusty Russell and Gert-Jaap, the topic of whether to allow for the use of sub-satoshi units in Bitcoin was discussed. Russell argued that allowing such units would render the network inoperable since fees are often sub-satoshi. He also expressed concern about moving away from the limits of the base layer and potentially compromising security. Gert-Jaap countered by suggesting that users should be allowed the freedom to choose their preferred unit of account, even if it means sacrificing some level of trust. He proposed further analysis on the consequences of such a choice and a concrete proposal/RFC to the spec. Ultimately, the discussion aimed to "test the waters" and gauge potential support for including this choice in the specification.