This is the existing WAL + cache implementation. Moving it to a separate file
so that it can remain intact while a refactoring to a independent WAL can occur.
The WAL was also named Log in the code so this names file more closely to the concept
in the code.
Float values are not supported in the existing engine and the tsm1
engines. This changes NewPoint to return an error if a field value
contains a NaN field. It also allows us to validate fields to prevent
other unsupported types from sneaking in through other input plugins.
Jason Wilder
Ben Johnson
Paul Dix