Unable to override (global) templates

[ArneMis]

I do not know how to create a pull request, so adding this to issues:

It would be nice to add a "templates" property to allow the user to override the global templates for some types.

Code change in FormSchema.js

var defaultTemplates = require('tcomb-form-native/lib/templates/bootstrap'); // -> NEW

type Props = {
data: Object,
schema: Object,
stylesheet?: Object,
templates?: Object // -> NEW
};

options: {
...getFormOptions(props.schema),
stylesheet: props.stylesheet,
templates: Object.assign(defaultTemplates, props.templates) // -> NEW
}

This is just an example how to implement this, maybe there is an even better solution.

const templates = {"select":select};
...

Thanks in advance