fix compile of some patricia_trie members

(which were never instantiated before.. glad I'm cleaning it up
and testing it now!)
move long patricia_trie member functions to .cpp
improve dev-build.py
add some notes about how to release well to DEVELOPER_README
Give worldblock impl its own header file.
tests: improve display of exceptions
add patricia trie tests and docs
patricia_trie: stop using 'siblings' member

It wasn't gaining us any performance (per testing),
which was its only reason for existence, and it uses up
memory space and code complication.  To be removed entirely in
next commit.
remove siblings_ member from patricia_trie

This didn't make much perf improvement but it simplifies the code
and is harmless.
test patricia trie bounding boxes
patricia_trie: abstract out the implementation so I can change it better

It was/is a kind of hacky implementation for the purpose of
saving RAM, and it might remain kind of hacky for that purpose
or might not.
Merge branch 'master' of https://github.com/elidupree/Lasercake
mention test failure
fix new patricia_trie code
When debug drawing, draw the worldblock trie.
Enable OpenGL depth test.

This is necessary for the worldblock trie to look understandable,
and probably harmless otherwise.  We can do better, of course.
make debug display mode also display the objects collision detector
remove obsolete typedef
explain comment more
patricia trie representation: remove unjustifiable hack