Configurable default folding depth.

[kiith-sa]

Currently, every package in the TOC tree is folded by default (if JavaScript is not disabled).

This is not always user-friendly, e.g. when using a few nested packages in a parent package, this adds an extra click.

Add a config variable in hmod.cfg/CLI to specify the nesting level where to start folding by default.
E.g. foldedDepth = 1 will mean the top package/s will not be folded but any subpackages will,

And implement the code needed for this to work.