FEATURE REQUEST: Config file writing.

[DevGIB]

I brought it up on discord but i figured i'd post here too.
It would be good to be able to enable or disable a package from within escript/pol itself.
Turley suggested that we write to the pkg.cfg file, however there is only the option to append to a config file, not update or write new values.
I assume potentially we could use ReadFile() and WriteFile() but i'm wondering if there could be an easier way from within the CfgFile.em given that it has the facility to read files as elements.