Blender Git Loki

Exporter: Fix UV indices being edited by the writer.

Also revert
{{rBd68899e99a0c}}

Importer: Fix misaligned UV vertices of a mesh

The previous code was not initialising duplicate UV vertices which
created bad shapes in UV editor.

Also use range-loop.

Also since set_uv needs not be edited, mark curr_object const again.

Exporter: Fix freeing invalid pointer in ~OBJMesh

Merge branch 'master' into soc-2020-io-performance

Fix UV crashes and redundant loops in v1//vn1 case.

Importer: Support smooth shading for polygons.

Exporter: fix vertex normals not being exported

The smooth group calculation must be done before normals are
written, to decide between vertex normals and face normals.
So moved the smooth group array in the OBJMesh's private members.

Null check: Break if no UV layer found.

Also conditionally add an UV layer, not always.

Add UV vertices to the newly created mesh.

The mesh->mloopuv has the correct vertices, however it hits
the assert at `(uniform), function GPU_batch_uniform_4fv,`
`blender/source/blender/gpu/intern/gpu_batch.c, line 617.`
if one switches to UV editing workspace.

Exporter: Fix UV vertex indices off by one.

Cleanup single use variable, comments, formatting

Also, vert_texture.size() was wrongly compared to 1. It's changed to 2.

Use stoi and stof instead of >> for faster parsing.

Parse UV coordinates and normals.

Adding UV to the mesh is not done yet.
Using `std:stoi` seems to add some benefits, so UVs will be added
to mesh after parser is complete.

Merge branch 'master' into soc-2020-io-performance

Directly create Mesh without using intermediate BMesh

Refactor: Keep mesh_from_raw_object in a class

The function is moved to a class for a self-contained mesh operation.
BMesh operations will not be required without a mesh first, so they
should be kept in a Mesh operation class.

Remove unused variable: bmain

Keep classes ordered as per Style Guide.

Pass object_name to add_object_to_parent since only that is required.

Fix build error in due to BKE_mesh.h

Rename files: exporter -> ex, importer -> im.

Minor header cleanup.

Break code into mesh, objects, and reader files.

clang format, style: use {} initialization, nullptr.