Refactor floorplan grammar

[argenos]

Most of the changes are documented in docs/v2-motivation.md. As a very short summary, not exhaustive and in no particular order:

• Renames the python package from exce_floorplan to floorplan_dsl
• Reorganizes the repository to minimize code duplication and allow for easier code reuse/refactoring. As much as possible, tried to organize v2 by concern: semantics, validation and scoping have their own modules. v1 is still included in this repository until it can be fully deprecated (e.g. Refactor the 3D mesh and occupancy grid generation #11 has also been closed).
• Redesigns the floor plan grammar and the custom classes from scratch
  • Includes concepts and semantics necessary for the JSON-LD generation
  • Improves the concrete syntax to remove the need to define translations and rotations of zero in locations of various floor plan elements
  • Makes the specification of locations consistent across elements
• Adds a converter from v1 models to v2 using Jinja templates textx generate models/examples/hbrs.floorplan --target floorplan-v2 -o models/examples --overwrite
• Reorganizes and redesigns the Jinja templates for the JSON-LD generation to maximize their reuse
• Updates the Variation DSL to work with v2
• Adds missing elements to JSON-LD models: features and openings were missing in several models
• Fixes the prefixes in the JSON-LD context so they no longer point to the metamodels
• Fixes the coordinates.json to follow the schema in the kinova models
• Changes the internal representation of angles to RAD instead of DEG
• Adds an additional argument to generate the JSON-LD coordinate pose angles in degrees instead of radians
• Moves the README.md and images to the docs folder to allow GH pages to see and use them.
• Updates the JSON-LD coordinates.json to use the appropriate QUDT units (i.e. DEG instead of degrees)

Note that the blender export won't work any more (it is untested) but will be removed soon from this repository (see #11 )