Add file modes to types/global.h
Add wf_get_option() to src/worldfile.h
Add world parameter to wf_read() and wf_write() in src/worldfile.h
Chenge return type of wf_read() to int
Move file modes to types/files.h
Add implementation of worldgen (src/worldgen.c)
Add implementation of worldmem (src/worldmem.h)