Improve `rake upgrade` error messaging when used incorrectly

[#64936304]
When installing templates, clean up old templates but only ones actually belong to Cedar.

- A template is determined to belong to Cedar if it either 1) includes a "isCedarTemplate"->"true" entry, or 2) has an "Identifier" entry beginning with "com.pivotallabs.cedar"

[#64936380, #68661790]
Use an Xcode text placeholder for the SUT variable name in the Cedar Spec file template