Add timestamp/datetime to snapshots (replacing ID).

Closes #6.
Automatically create snapshot each time the project is changed
Fix datetime column in snapshot window
Merge pull request #13 from rsnitsch/master

Undo feature completion
fix testsuite building
use boost::filesystem for more portability
remove unused function
remove get_temp_directory(), as we are using boost::filesystem::temp_directory_path() now
stop polluting console with glyph-cache debug
use debug for debug messages
use iostream instead of printf for increased portability
remove get_temp_directory from header
add get_data_dir helper with sane default set by cmake
use get_data_dir instead of getenv
add install cmake target. now degate can be installed system-wide
Merge remote-tracking branch 'origin/master'