Improved support for Launchpad Pro MK3

[Xpktro]

Recently bought a Launchpad Pro MK3 as the Readme stated it was supported. Was puzzled when it didn't work automagically at first. I discovered two things:

• My launchpad was being listed as Launchpad Pro MK3 1 in the MIDI devices list, but the mapping was expecting a non-numbered name.
• This model would require setting Programmer Mode by holding Setup + the Lowest Launch button. The official programmer reference explained it could also be set by sending a specific message, which the library was lacking.

This PR addresses both situations detecting numbered Launchpad MK3 names and setting the appropriate init Programmer Mode message.