Function encodeShape

encodeShape(cache, shape): number
Create shapes

Used by Layer's and Feature's M-Values Must be an object of key values all keys will be the same, values will be different A layer's Shape defines what the properties look like for every Feature in that layer so we only have to store the properties and M-Value shape once per layer.
Parameters
- cache: ColumnCacheWriter
  the cache where all data is stored in a column format
- shape: Shape
  the shape object to encode
Returns number
- The index of where the shape was stored in the cache