Add fields to db

[zoobot]

scientific: full botanical name
genus: scientific genus (eg Melaleuca)
species: species epithet (eg linariifolia)
variety: everything that comes after species, including cultivar, variety etc.
crown: width of crown, in metres

MBG_ORIENTATION ( type: esriFieldTypeDouble, alias: Crown Orientation )
MAX_CROWN_HEIGHT ( type: esriFieldTypeDouble, alias: Crown Height Max )
MAX_MEAN ( type: esriFieldTypeDouble, alias: Crown Height Mean )
MIN_CROWN_BASE ( type: esriFieldTypeDouble, alias: Crown Base Min )
DTM_MEAN ( type: esriFieldTypeDouble, alias: Ground Elevation )
PERIM ( type: esriFieldTypeDouble, alias: Crown Perimeter )
CROWN_AREA ( type: esriFieldTypeDouble, alias: Crown Area )

(https://github.com/waterthetrees/wtt_area/issues/28)[https://github.com/waterthetrees/wtt_area/issues/28]