[rtree] Implement a STR-R-Tree for bounding box querries.
[utils] Added archive format and save serilation and leafs in it
[geodata] Allow empty datasets
[kdtree] Remove kdtree since it is replaced by RTree
[tests] Moved kdtree-test to geodata-test
[geodata] Rebuild temp file handling for leaf files
[archive] Add padding to blocks in archive.

This is needed to mmap the archive dirctly to memory and adress files by
offsets.
[RTree] Use mmap instead of a file handle.

seek + read is not atomic, thus not thread-safe. mmap is faster and
reads are atomic.
Merge pull request #32 from alacarte-maps/rtree

Rtree with backing storage