Update code generator

[yaegashi]

Current msgrpah-generator.go cannot handle the latest API specfication.

Support Alias attribute (in v1.0 and beta):

<Schema Namespace="microsoft.graph" Alias="graph" xmlns="http://docs.oasis-open.org/odata/ns/edm">

Support different Namespace other than microsoft.graph (in beta):

<Schema Namespace="microsoft.graph.callRecords" xmlns="http://docs.oasis-open.org/odata/ns/edm">