Update in_01_horizon_names.qmd

- add note on removal of L horizon
- minor wording tweaks in preamble
- consistent time units in organic horizons
- relate R horizon concept to degrees of weathering defined earlier
- add note about lack of secondary C and R subdivisions
  - remove separate R horizon section - pointless
- add table of common transitional horizons
- update some horizon definitions to more closely align to NZSC (work continues)

Author: lauren-obrien