Fix typo and cleanup

The 'raw' identifier cannot be resolved; it should have been to be
'raw_data'.

Get rid of multiple compilation modes (fast vs accurate) and expose
the configuration through env variables.
Simplify "building" steps and fix "running" examples

The library does not have fast/accurate build option anymore.

The ArrayBench.dll library does not exist; ArrayBench.fs compiles into
ArrayBench.Core.dll (which evaluates the performance of FSharp.Core
functions) and ArrayBench.Impl.dll (which evaluates the implementation
given in the source).