v2.6.16 - performance enhancements

[Kyle]

Thanks to user @DennisKriete for finding an increase in CPU load between v26.12 and v2.6.13. This was partially due to changes in debug logging.

Changes in this release:

• There is now a compile time minimum logging level. This eliminates SPEW level logging on Debug builds and DETAIL and SPEW on production builds. The logging statements are compiled out and removed as dead code by the compiler.
• There are tools to measure performance more accurately as well as efficiency.
• The Modbus code has been modified based on the perf measurements. The AB code is next but requires much more work than Modbus. AB code is not changed in this release.
• Some core vector functions and reference counting functions have been updated to use far less CPU as well as generally lowering the number of times the functions are called. There is more to do here.
• Increasing efforts (not fully complete) to completely eliminate any compiler warnings.
• fixes for the issue noted by @chenrui333 with compilation warning.
• Added AI policy explanation document.

I have added some new performance graphics. See attached.  

Get the release from the usual place.

Best,

Kyle