Option to change the ErrorText color from the de

[marcus905]

Feature Request:

Add the option of changing the ErrorText color. Adding another BindableProperty, in iOS it should then be trivial, in Android it's a matter of resolving the reflection needed to set as it's a public field that's not included in the standard SDK, but there are people that accessed it like here in StackOverflow (https://stackoverflow.com/a/34752605 https://stackoverflow.com/a/35015792).

It's not included in bug #6 so I thought it was appropriate to open another one.