extractSMR updates

[brownag]

Add other wet suborders and SMR described only at subgroup level.

1. Suborders of Histosols other than "Folists" (Fibr-, Hem-, Sapr-) imply at least "aquic" moisture regime. These have been added. "wass" formative element used in suborders of Histosols and Entisols are now handled as the only current route into "peraquic" moisture regime.

2. For taxa that have no information about soil moisture regime at order to great group level it is valid to use the subgroup-level information, if present, to assign SMR.

   • Commonly subgroup level moisture formative elements are referring to a moisture subclass or are re-stating the class of the parent taxa.
   • If there is a higher-level connotation available (i.e. great group to order level) the highest level is always returned by extractSMR(). In the cases where there isn't a higher-level connotation the subgroup does imply the SMR.

library(SoilTaxonomy)

extractSMR('ustic haplargids')
#> ustic haplargids 
#>  aridic (torric) 
#> 7 Levels: aridic (torric) < ustic < xeric < udic < perudic < ... < peraquic

extractSMR('ustic haplocryolls')
#> ustic haplocryolls 
#>              ustic 
#> 7 Levels: aridic (torric) < ustic < xeric < udic < perudic < ... < peraquic

For the future: dealing with parsing soil moisture subclasses via an additional option would be a great new feature, but they have more complex rules depending on the order/suborder they occur in. e.g. Aridic Mollisols have the subclass in the suborder. Currently extractSMR() is not aware of these types of relationships within taxon names and would need a more detailed set of rules or lookup table to handle these cases.

[brownag]

New issue #49 to further handle subclasses. The approach here for partial matching can lead to some ambiguity if not filtering to just the highest level formative element related to moisture regime.