Fix to prevent crashes

Add support of raspberries and blueberries from farming redo

Fix some indented lines from spaces to tabs

It doesn't work well because of the special on_place.

Minetest Game has waterlily now, so we need to load after it to override
its node definition.

Conflicts:
	nature_classic/init.lua

so simplify and revise it to act as a "3d-ify" mod for them.

Unidenfied spores aliased to the regular default equivalents
poison and essence aliased back to their originating mushrooms
identifier aliased to mese crystal (most expensive component of it)
everything else aliased to their default counterparts

spores are not dropped from digging dirt with grass anymore

renamed it to biome_lib
changed all relevant functions, tables, depends.txt, etc. in this modpack to call for the new name.

(for Realtest compatibility)

At the previous rate, it would take almost 27 days for half of the
short grass to convert to regular dirt with grass. And therefore
54 days in total to reach 75% conversion, 81 days for 87.5%, etc.

At the new rate, it should take about 4.5 hours for half of the
short grass to convert back to dirt wit grass.

At the previous rate, it would take almost 2 days and 15 hours of
playing time for half of the reedmace to grow. (and therefore 5 days
and 6 hours for 75% to grow, etc.)

The new rate should require 2.25 hours of playing time for half of
the reedmace to grow.

As there is only one leaf per fern, this makes it possible and convenient
to farm ferns (which was impossible, and even replanting all chopped-down
fern plants was extremely laborious due to the rarity of saplings).

Although on average slightly more than one sapling is produced per plant,
replanting and reharvesting the leaves is still the quickest way to
obtain more saplings.

This happens when the ABM runs after the block has been unloaded
for much longer than the ABM interval: in that case, the initial
ABM running chance for a node in the block may become up to 100%.

Because minetest.after() is not bound to a position, and because it is not
saved, it may trigger after the node to which it applies was unloaded, or
not at all (if the session ends). If that happens, The 'young' flag
will not be cleared, and will have become persistent (i.e. without a timer
which will eventually clear it).

This patch removes the 'young' flag, and replaces it with a timestamp, removing
the need for a timer. Any lingering 'young' flags that have become persistent
are automatically removed over time (i.e.: they are simply ignored...)

It didn't, so that all apple leaves would permanently become blossom
over time.

Fixes documentation 

See related discussion #49.