Refactor tracklog code

[M4rtinK]

The current tracklog handling (recording/storage/loading/display) is one huge mess - the code was written long ago and is pretty bad. Now I know better so it's time improve it:

• moving more stuff to core & adding unit tests for it
• one modRana module is probably enough for tracklog handling
• there have been some ideas for having smaller modules, but having 3 (or more ?) full modRana modules just to handle tracklog is a bit too much
• PEP8 compatible code
• using properties where possible instead of getters
• dropping tracklog point clustering and using route segments with bounding boxes should be overall better