MIDI Learn: support for 14 bit resolution using MSB/LSB CC# pairs / (N)RPNs / pitch bend

When using the Param > Learn feature, one or more options should be added for MIDI in 14-bit resolution. There are various MIDI data types that use 14-bit resolution:

- MSB/LSB CC# pairs (CC# 0-31 for MSB + CC# 32-63 for LSB);
- (N)RPNs;
- Pitch bend (even though most physical pitch bend controllers do not fully utilise the entire available resolution).

Currently the only option for absolute control uses the regular 7 bits resolution for single MIDI CC#s. Thus, it does not seem to be possible to use such high resolution MIDI control schemes for controlling parameters in REAPER directly (i.e. without external tools or workarounds), while the limited resolution of 7 bit CC#s does not suffice for many parameters.

For some examples of use cases, controllers, instruments, and plug-ins that would benefit from this:
- When controlling track volumes or ReaEQ frequencies (especially when boosting a very small bandwidth) using a MIDI controller, 128 steps is much too grainy, and results in audible 'stepping'. We really need options for more precise control.
- U-he's Zebra2 and Diva plug-ins support 14-bit MIDI CC# pairs (these are also quite popular);
- Behringer BCF-2000 / BCR-2000 controllers can send 14-bit MIDI CC# natively (judging from the amount of related posts on this forum, many of us REAPER users have these);
- The Moog Little Phatty / Slim Phatty synthesisers are able to send/receive 14-bit MIDI CC# pairs (since OS 3.1) as well.

Discussion thread here.