New meta in LDConfig for default category icon in editors

[Roland Melkert]

!MASCOT CATEGORY "<category>" DESCRIPTION "<description>" PART <rotation maxtrix> <part file>

I'm ok with avatar instead of mascot.

Not sure about loosing the quotes around the part file though. It's true the spec forces whole words but that is the current spec. Also it seems more consistent to use it for all string variables. That said it's not really a show stopper for me so I'm ok ether way just my 2cts.

nitpick:

If a !MASCOT statement for a given !CATEGORY is not present, then the mascot may be chosen by the developer

This sounds a bit preachy, imho, maybe:

If a !MASCOT statement for a given !CATEGORY is not present, then the selection of the mascot is entirely up to the developer

Because meta or not the developer can choose not to use them at all, the 'may' suggests it MUST be used.