Todo before v2.0 alpha release

[cwhanse]

• adjust schema models for rack, table and table_group Move tilt, azimuth etc. to rack from table #27
• add schema model for post Models for post and gap #29
• add schema model for gap Models for post and gap #29
• add schema models for tracker and instance_tracker Add tracker product data model #30
• [ ] add schema model for fence Deferred until requested by an adopter
• consider if cable_to_parent should be added to module_array_type move cable_to_parent to module_array #28
• add example showing how to use a second technique
• add example showing how to use rack, table, table_group and tracker Updates of example files #32
• documentation: explain where PVCollada adds to the major sections of a COLLADA document: asset, geometry, node
• documentation: explain coordinate convention PVCollada convention for North/East orientations #1, and provide guidance on use of rotation PVcollada convention for rotations and translations #3
• Use geographic_location #23 and explain in convention in documentation
• versioning: rename pvcollada_schema_0.1.xsd to pvcollada_schema_2.0.xsd
• clean up working files
• update or remove examples 01 through 04 Updates of example files #32
• rename examples to drop e.g. "v3" Updates of example files #32