Fixed bug when serializing a color on some locales.

[EmKayDK]

This bug caused the decimal separator to be comma instead of a dot.

Resulted serialization was for example "0,4901961,0,4901961,0,4901961,1". With this fix it is the correct version "0.4901961,0.4901961,0.4901961,1".

How to reproduce:

• Set computer to danish locale (or other locale with comma as decimal separator)
• Follow tutorial at https://koyoki.github.io/marklight/docs/tutorials/gettingstarted.html until "Adding View Actions".
• Set theme to Flat and let the views reload.
• Inspect the first button and in the Button (script) component find View Field State Values. Expand this and expand the second ImageComponent.color. The value of this property should be "0,4901961,0,4901961,0,4901961,1".
• When running the game an exception is thrown on startup and when triggering mouseout on the button.

[patrik-u]

Thank you for your commit 👍