LWO fixes

[turol]

Cleans up LWO loader a bit, adds debug logging and closes a bug that prevented loading LWOB files. I'm not entirely sure if this is the right fix but it seems to work.

Closes #1196

[turol]

@tellypresence @darkf Please test if this works for you.

[kimkulling]

Looks fine for me. Indeed, the loader seems to need some more love and refactoring.

[kimkulling]

Merged, thanks a lot for your contribution.

[turol]

Yes, this loop:

assimp/code/AssetLib/LWO/LWOLoader.cpp

Line 630 in 9033334

for (auto itMapParentNodes = apcNodes.begin(); itMapParentNodes != apcNodes.end(); ++itMapParentNodes) {

Looks suspiciously O(n^2)
However currently nothing triggers pathological behavior and it's really hard to understand what's actually happening here.