Merge pull request #35 from Mixaill/master

Fix CMake confuring on Windows after #29
[style] Use float instead of double to reduce memory consumption
[renderer] Added virtual destructor to writer to fix leak.
[debug] Added class to count objects in memory for debugging
[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
[doc] Updated readme.
[geodata] Fixed import when some objects are not used
[build] Updated Log4Cpp macro names
[build] Export compile commands for vim plugin
[build] Ignore YCM and git-bibisect config files.
[build] Fix for old log4cpp versions
[utils] Changed min. PAGE_SIZE to 64k for Windows 64bit systems