In commit 95b4198e2ca1cba037cb46bdfda8f10ed334b565 the AudioProcessor interface functions valueFromString and stringFromValue have just been removed; however they should have been used in the AAX and RTAS wrapper, for instance in GetParameterStringFromValue, for displaying the right value when editing the automation in the DAW. They can also be used for other purposes, for example from the plug-in UI. So I suggest a total/partial revert.
No - they only ended up in that class by accident. There are already string conversion methods in AudioProcessorParameter which do the same job, and AAX already uses those to implement this. Sorry for the confusion!
I know, but that old method is only kept there for backwards-compatibility with old code.
New parameter functionality all belongs in the AudioProcessorParameter class, and I'm not going to make the already-too-bloated AudioProcessor class even messier by adding methods that are duplicates of the ones in AudioProcessorParameter!