TaxRate to BigDecimal?

[schleichardt]

@lauraluiz what do you think? http://sphereio.github.io/sphere-jvm-sdk/apidocs/io/sphere/sdk/taxcategories/TaxRate.html#getAmount--

[lauraluiz]

In case of doubt I always use BigDecimal, especially since it is normal to do mathematical operations with the taxes, so yes from my side :+1:

[schleichardt]

I will add another method to stay compatible with current sdk users.

[katmatt]

I would prefer to change the getAmount method to return BigDecimal instead of Double. That's a breaking change, but as suggested by Michael we could add another method getAmountAsDouble to make it easier to migrate existing code.