Remove deprecated CIF Features

On the 7th of July in 2021, ESCET Version 0.2 was released. In that release the following features were deprecated:

CIF deprecated enumeration declaration syntax (with curly brackets) now leads to deprecation warnings.
The documentation now properly reflects the deprecation as well (issue #45).


CIF to CIF transformation to eliminate enumerations (elim-enums) is now deprecated.
Use the transformation to convert enumerations to integers instead, as it has the same functionality (issue #78).


CIF PLC code generator option to either eliminate enumerations (to integers) or not is now deprecated.
Use the new option to choose whether to convert enumerations to constants or integers, or not at all.
See the documentation of the PLC code generator for further details (issue #78).

At the time, we weren't sure how long we should support deprecated feature. I think two years is more than reasonable for these, as they all have very easy-to-implement alternatives for users.