Task: update examples section for v2.0RC2

[donmendelson]

Update the example sections for changes in SBE 2.0 RC2.

[gelupa]

The example section in SBE 1.0 is still unchanged. The most significant error is there are only 4 fields, instead of 6 fields of SBE headers in the example.

[donmendelson]

I have code to generate examples in project FIXTradingCommunity/fix-sbe-examples. I'll merge output into the spec when most issues are settled.