This was a rather easy change, since only parameter names make use of
strings in the first place.
This also improves OOM resistance: If we can't create a parameter name,
we will just set it to the empty string.
We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
If the underlying parameter is logarithmic, the slider respects that and
switches to a logarithmic display. Currently, the used base is e, and
we'll have to see in practice if 2 or 10 might be better. The parameters
that make use of this, as can be seen in the previous commit, are all of
the time dependent parameters such as the synth envelope parameters, as
with these, usually fine-grained control at small time scales and
coarser control at large time scales is desired.
This was a good opportunity to refactor the slider step count into a
constant.
