Function writeOVLayer

writeOVLayer(layerCache, pbf): void
Because of the Column Cache, a layer will contain:
- version 1 byte
- extent (1 byte) - 1 -> 1024, 2 -> 2048, 3 -> 4096, 4 -> 8192
- name (varint) - index into the string columns table
- features (writeMessage) - for each feature
Parameters
- layerCache: {
      cache: ColumnCacheWriter;
      layer: BaseVectorLayer;
      verbose: boolean;
  }
  object containing the layer and the cache
  - cache: ColumnCacheWriter
    the cache where all column level data is stored
  - layer: BaseVectorLayer
    the layer to encode into the Protobuffer
  - verbose: boolean
    set to true to print out write information
- pbf: Pbf
  the pbf protocol we are writing to
Returns void