TheWeatherCompany/grid-api#1212 Add support for instance-store/ephemeral drives.

PR for TheWeatherCompany/grid-api#1212
Hi @clstokes one more q. Am I right that we need to return ephemeral store as VolumeProduct in Iterable<VolumeProduct> listVolumeProducts() method [here](https://github.com/TheWeatherCompany/dasein-cloud-aws/blob/ccd16662e7ac31dec46c81e58865525c24a172c9/src/main/java/org/dasein/cloud/aws/compute/EBSVolume.java#L278-L280)? if yes, is it OK if value will be defined as ```prds.add(VolumeProduct.getInstance( VOLUME_PRODUCT_EPHEMERAL, "Ephemeral", "Ephemeral storage", VolumeType.EPHEMERAL, getMinimumVolumeSize(), "USD", 0, 0, 0f, 0f);```. Please note that _EPHEMERAL_ value will be added to VolumeType enum then.