Move quad_tile.cpp

quad_tile.cpp is specific to apidb backends, so move it there
Fixed issue #16, treat 0 or negative user IDs as anonymous users.
Remove version number from README header, was wrong.
Merge pull request #15 from pnorman/quadtile_move

Move quad_tile.cpp
Refactor row/tuple dependency out of formatters and lift into the backend.
Merge branch 'master' into snapshot_nodes

Conflicts:
	src/Makefile.am
wip
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