[OSD] Check for empty sections and duplication of section content under wrong header

[brownag]

For example, ADEN soil series:

SoilKnowledgeBase/inst/extdata/OSD/A/ADEN.json

Lines 32 to 39 in e9946b1

	"GEOGRAPHICALLY ASSOCIATED SOILS": {
	"section": "GEOGRAPHICALLY ASSOCIATED SOILS",
	"content": "GEOGRAPHICALLY ASSOCIATED SOILS: These soils are associated dominantly with the Bermudian and Roland soils of the flood plains and the Arcola, Nestoria and Reaville of the uplands. The well drained Bermudian and the moderately well to somewhat poorly drained Roland soils are on slightly lower elevations in the landscape and have thinner and coarser textured subsoils. The Arcola, Nestoria and Reaville are developed in residuum from silt stone and sandstone and are shallower to bedrock. DRAINAGE AND PERMEABILITY: Poorly drained. Slow runoff and slow internal drainage."
	},
	"DRAINAGE AND PERMEABILITY": {
	"section": "DRAINAGE AND PERMEABILITY",
	"content": "GEOGRAPHICALLY ASSOCIATED SOILS: These soils are associated dominantly with the Bermudian and Roland soils of the flood plains and the Arcola, Nestoria and Reaville of the uplands. The well drained Bermudian and the moderately well to somewhat poorly drained Roland soils are on slightly lower elevations in the landscape and have thinner and coarser textured subsoils. The Arcola, Nestoria and Reaville are developed in residuum from silt stone and sandstone and are shallower to bedrock. DRAINAGE AND PERMEABILITY: Poorly drained. Slow runoff and slow internal drainage.\nDRAINAGE AND PERMEABILITY:"
	},

Geographically Associated Soils section is repeated as the content for GAS and Drainage and Permeability (which is present, but completely blank in the source data). This results in parsing the "well drained" phrase from GAS as the drainage class for the series. Luckily drainage class (poorly) is also in the overview section in this case, which is what alerted me to the problem.

OSD	JSON
ADEN	ADEN.json

At this time it is not clear how many other instances are affected by this type of error; it might be fairly common wherever "empty" sections occur.