Deprecating ifvarclass

We should deprecate ifvarclass in favor of if:

• if is a much better name, ifvarclass is confusing to a new user and generally harder to read
• consistency is good, all examples, documentation, and generally policy that people see should use the same name
• The "alias" has caused a few bugs, because aliases of promise attributes are not really implemented in a good way

However, we will need to keep backwards compatibility for a long time.

What should be done:

• All examples should be updated to use if
• Most tests should be updated to use if
• masterfiles should be updated to only use if
• Documentation should be updated to clearly state that ifvarclass is not just an alias, but also deprecated and should not be used.