v2.7 : updates to API functions and macros

No change to the character sheet.
Updates to the API functions (NathasNumenera_Roll20_API.js) and macros
(NathasNumenera_Roll20_Macros.md) :
1. New function/macro to apply damage to NPC
2. Update to the stats rolls (function and macros) : now handles damage
effort and the chat output has been improved.