bump ClassTemplate version constraint

Checking in changes prior to tagging of version 2.1.2.

Checking in changes prior to tagging of version 2.1.1.

Checking in changes prior to tagging of version 2.1.0.

include codegen ~2

Checking in changes prior to tagging of version 1.4.5.

Checking in changes prior to tagging of version 1.4.4.

Checking in changes prior to tagging of version 1.4.3.

Checking in changes prior to tagging of version 1.4.2.

Checking in changes prior to tagging of version 1.4.1.