Support bone parenting, improved merge
If the exported object parent is a bone, skin the mesh to the bone with
a 100% weight. (for big meshes it's better to do it without skinning)
When merging more objects avoid decomposing armature and animations
one time per object.
Moved the cobject transforms checks to the armature decompose and limit
them to the exported object (not to all the armature children).
Should: fix #2, fix #8.
Added only deform bones, only visible bones options
With these options bones without Deform or bones not visible are
not exported in skeleton and animations. Also all their children
are not exported (must preserve bones hierarchy).
Added some options relations.
Set more reasonable default values.
When merging the current object must be a mesh to use its name.
Review morph vertex comparison, now it compares only elements (pos,
normal, UV) which are not None.
Added more severe rules on writing file array values.
For morphs only write position, normal and tangent, not UV.
Corrected bug on morph tangent function parameter, and bug on writing
morph tangent, file were corrupted by the extra float of tangent.w.
Fix #4, fix #9
Added material text list
Deleted too strict options relations
Fixed wrong type
Fixes #11
Again on rest position
'.pose_position' does not seem able to restore the vertices positions,
so try going in and out edit mode. A bait for crashes...
Do not export hidden objects
Added merge for LOD, changed LOD parser
Now it possible to merge multiple objects and use LODs together. All
materials should be present in each LOD, in this way each geometry has
the same range of LODs, otherwise, if some LOD is missing the following
LOD will extend its range to lower distances and it can overlap other
geometries.
Revised all the LOD creation, instead of a bool it uses a set() to keep
track of what geometries are updated with the last LOD.
On the LOD object names, it is no more necessary for the distance to be
right aligned; also, if an object name is missing the _LOD tag, it is
considered as the first LOD with distance 0.
Added an option for keeping the materials separate in different geometries
while merging objects.
Keep separate object name and Blender object name.
Added 30° limit for normals in not strict LODs
A not strict LOD will try to find the most similar vertex, but it was
even adding vertex with flipped normals.
Now there is a limit of 30° between normals, if no vertex is found a
new one is added (a warning signals it).
Cleaning
Fixed UI error
Geometry order now defined by material slot order

Material export now binds one-to-one with blender materials (i.e.
show_double_sided from the blender mesh is no longer used).  This flag
has been moved to materials as "double_sided" (if only because I
couldn't work out what to do when you have two meshes using the same
material, with one being double sided and the other not).

Shadeless materials have also been added (they use the Unlit
techniques). NOTE: specularity is ignored if shadeless is true.

We now create a geometry per material slot (even if that material isn't
used) - this is to give us predictable behaviour in Urho (slot 1 in
blender == slot 1 in Urho).
Sort vertex weights during decomposition

Vertex influences are now sorted (and capped to 4) during decomposition.