To visually match the 1 node per second spread of flowing water.

Papyrus was missing from the dry dirt 'savanna_shore' biome due to
only being placed on dirt. A mistake made when changing savanna
dirt to dry dirt.

Rename existing papyrus schematic to 'papyrus_on_dirt' and only
place in the 'rainforest_swamp' biome.
Add a new papyrus schematic 'papyrus_on_dry_dirt', placed in the
'savanna' biome.

rail = 轨道 / 栏杆
grass = 草

and, mese color is yellow, so i translate it to "黄石"。（Chinese words without MESE）

This allows mods to easily implement the same behaviour, e.g. for letters.

In preparation for a new Mapgen V7 floatland implementation.

Previously, papyrus was limited to the savanna biome.
Rainforest is a suitable habitat for papyrus.
Makes papyrus a little less difficult to find.
Move swamp jungletrees into a separate registration, to allow
applying distribution by perlin noise to keep these away from
papyrus areas.

Fix error: Remove non-functional 'rainforest swamp' from the
biome list for the jungle log decoration. It is not placed in
swamps due to the 'y max/min' and 'place on' parameters.

Implement drag force according to the equation:
drag_force = drag_coefficient * speed ^2
Also add a small constant force to implement friction force.

These are unrelated to the Player API and player object.
All other GUI/HUD code and textures are in default.
All other engine hardcoded sounds are in default.
The player_api mod is highly likely to be used unchanged in new games,
so logical grouping of content will help the creation of new games.