Update of schemes & scheme_types data sources (MNE)

[florisvdh]

• regarding _Groundwater monitoring: environmental pressure 05.1_desgw, type 8310 has been put in its own, separate scheme because it cannot have the same environmental variable as the other types of the terrestrial scheme. We end up with three schemes here: terrestrial, aquatic and caves...
• for all distinguished typegroups (i.e. grouping of types within a scheme), English & Dutch names and shortnames have been added. (More languages can be accommodated.) With credits to @w-jan for proposing names of the _GW_05.1terr typegroups.

You can explore and use this after installing the package (see README for the install_github() command, but add the ref = "typegroups" argument):

schemes_en <- read_schemes()
schemes_nl <- read_schemes(lang = "nl")
scheme_types_en <- read_scheme_types()
scheme_types_nl <- read_scheme_types(lang = "nl")

# inspect the different schemes with and without typegroups:
scheme_types_en %>%
  select(-type) %>% 
  distinct %>% 
  arrange(scheme, typegroup) %>% 
  View
# etcetera