Fix ToSvgString

[wieslawsoltes]

What does this implement/fix? Explain your changes.

The ToSvgString method used current culture which produces invalid path data on some culture (uses , instead of . for separator.

[mrbean-bremen]

Thanks - not the first time I see such an error!

[H1Gdev]

@wieslawsoltes
@mrbean-bremen

https://github.com/vvvv/SVG/blob/a6515547b5e49ee6844611d0423155c24199d434/Source/Paths/SvgPathBuilder.cs#L485-L496

I don't know which of way is good, but I think that it is better to unify either.

[wieslawsoltes]

Some example:

https://github.com/dotnet/wpf/blob/9f9c0426b33dee76319460e56f9f0459aee22206/src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/LineSegment.cs#L107

https://github.com/dotnet/wpf/blob/52f24ad1517fc4412c989ce684189d7249abd137/src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Converters/Generated/PathFigureCollectionValueSerializer.cs#L108

[wieslawsoltes]

Seems like SvgPathBuilder does not need to change culture after my latest PRs.

[mrbean-bremen]

I would prefer to always use the explicit invariant culture for float.ToString() and float.TryParse(), where the representation is fixed (as it is in SVG) - this is less error-prone IMHO.
So I like it the way @wieslawsoltes has done this, and I agree that the code in SvgPathBuilder can probably be removed (maybe can be added to the other PR).