Change fast internal types and document typedefs

[mborland]

Closes: #834

[mborland]

I still don't think using the fixed width types vs fast types is a good idea. Here are intel benchmarks:

With this:

===== Comparisons =====
comparisons<decimal32  >: 2055713    us (s=299999985)
comparisons<decimal64  >: 2354181    us (s=299999985)
comparisons<dec32_fast >: 660277     us (s=299999985)
comparisons<dec64_fast >: 565198     us (s=299999985)

===== Addition =====
Addition<decimal32  >: 2051498    us (s=1000134990395)
Addition<decimal64  >: 2424256    us (s=1000134990395)
Addition<dec32_fast >: 1619007    us (s=1000134990395)
Addition<dec64_fast >: 1108451    us (s=1000134990395)

===== Subtraction =====
Subtraction<decimal32  >: 1770480    us (s=166680686215)
Subtraction<decimal64  >: 2046855    us (s=166680686215)
Subtraction<dec32_fast >: 1424059    us (s=166680686215)
Subtraction<dec64_fast >: 879190     us (s=166680686215)

===== Multiplication =====
Multiplication<float      >: 77303      us (s=0)
Multiplication<double     >: 71929      us (s=0)
Multiplication<decimal32  >: 1749900    us (s=2500419801094285)
Multiplication<decimal64  >: 2104753    us (s=2500419770901035)
Multiplication<dec32_fast >: 829543     us (s=2500419801094285)
Multiplication<dec64_fast >: 773240     us (s=2500419770901035)

===== Division =====
Division<float      >: 100135     us (s=889346445)
Division<double     >: 104017     us (s=889346420)
Division<decimal32  >: 1907295    us (s=442402130)
Division<decimal64  >: 2330349    us (s=442402130)
Division<dec32_fast >: 934993     us (s=442402130)
Division<dec64_fast >: 1138186    us (s=442402130)

As is on develop:

===== Comparisons =====
comparisons<decimal32  >: 1881797    us (s=299999985)
comparisons<decimal64  >: 2351746    us (s=299999985)
comparisons<dec32_fast >: 618556     us (s=299999985)
comparisons<dec64_fast >: 521408     us (s=299999985)

===== Addition =====
Addition<decimal32  >: 2013988    us (s=1000134990395)
Addition<decimal64  >: 2473012    us (s=1000134990395)
Addition<dec32_fast >: 1248342    us (s=1000134990395)
Addition<dec64_fast >: 906706     us (s=1000134990395)

===== Subtraction =====
Subtraction<decimal32  >: 1788740    us (s=166680686215)
Subtraction<decimal64  >: 2045088    us (s=166680686215)
Subtraction<dec32_fast >: 1081617    us (s=166680686215)
Subtraction<dec64_fast >: 783670     us (s=166680686215)

===== Multiplication =====
Multiplication<float      >: 77166      us (s=0)
Multiplication<double     >: 72769      us (s=0)
Multiplication<decimal32  >: 1761256    us (s=2500419801094285)
Multiplication<decimal64  >: 2115496    us (s=2500419770901035)
Multiplication<dec32_fast >: 715356     us (s=2500419801094285)
Multiplication<dec64_fast >: 717914     us (s=2500419770901035)

===== Division =====
Division<float      >: 103752     us (s=889346445)
Division<double     >: 115549     us (s=889346420)
Division<decimal32  >: 1930520    us (s=442402130)
Division<decimal64  >: 2312833    us (s=442402130)
Division<dec32_fast >: 785470     us (s=442402130)
Division<dec64_fast >: 1270341    us (s=442402130)