Allow query by property alias

[ryantxu]

Fixes #98

This adds propertyAlias to the UI and query model for anything that accept it

Still totally untested since I don't know any real alias values to try :)

[atifali]

We have currently hardcoded the AssetProperty for this case that is used to form the frames in the backend. Will only work for floats as of now:

iot-sitewise-datasource/pkg/resource/sitewise.go

Line 31 in 8bbc4ee

if propertyAlias != "" {

[atifali]

this is one ad-hoc way to infer the dataType:

iot-sitewise-datasource/pkg/framer/property_value_history.go

Line 29 in 8751cee

property.AssetProperty.DataType = aws.String(getPropertyVariantValueType(p.AssetPropertyValueHistory[0].Value))

not ideal but works for now - will be nice to have the DescribeAssetProperty end-point working with propertyAlias only, and that way we could actually have all the other descriptions too - see: #98 (comment)

[ryantxu]

@atifali -- looks good! Since I created the issue, I can not approve it :)

[atifali]

see: #98