obsolete "solid layer" and rewire some of the terms under it

[cmungall]

We received a submission in NMDC where env_local was "solid layer". This is quite an abstract term that encompasses 83 varied terms like:

id	label	definition
ENVO:00000098	island	Area of dry or relatively dry land surrounded by water or low wetland.
ENVO:01000492	dung building floor	A dung building floor is a building floor which is composed primarily of dried animal feces.
ENVO:01001582	forest floor	Land which is present within a forest biome.
ENVO:00012408	aquifer	An underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) from which groundwater can be usefully extracted using a water well.
ENVO:00000271	chott	A dry (salt) lake in the Saharan area of Africa that stays dry in the summer, but receive some water in the winter. This water may come as a groundwater discharge.

...

Some of these may have some abstract similarities in being a layer of some sort but I think this is best captured as a PATO axiom and not a primary is-a classification

[pbuttigieg]

We can move the subclasses to other appropriate hierarchies, but solid layer should not be obsoleted. It can be filled by inference using the corresponding qualities.