Context Graph stages renamed

Context Graph stage names that referred to "Hub" in the 2020.1 release of Spectrum Technology Platform now refer to "Model", as listed in the following table.

Stage name 2019.1 and earlier	Stage name (2020.1)
Delete from Hub	Delete from Model
Import to Hub	Import to Model
Merge Entities	Merge Entities
Read from Hub	Read from Model
Query Hub	Query Model
Split Entity	Split Entity
Write to Hub	Write to Model