move closest-line-between from types.line ns into core.utils
remove obsolete fns from line ns, update references to moved fns in other types
update Rect type to new defrecord structure using Vec2 :size field
refactor index.org files for sub-modules, add config.org, add as LOB file for tangle.sh
update ns decl for rect ns
add supported types & operations overview to index.org
rename Path2 ctor