Fixed running MetFrag.NET on a PC that don't use a decimal point, e.g. French.

All the double.Parse calls have been updated to use CultureInfo.InvariantCulture when converting
floating point numbers from text. I also added to make sure it works with  various culture settings
that we've found to be problematic in the past.
More support of non-decimal-point cultures. I missed a few Convert.ToDouble calls.
Merge pull request #5 from NonlinearDynamics/MultiCultureSupport

Fixed running MetFrag.NET on a culture without a decimal point, e.g. France