make it possible to pass properties around

Most values that are read from .ini files are currently stored as a primitive type and not reloadable. 
I changed the way of how properties are stored to make it possible to pass Property objects around and create unnamed properties.
We can now change the important member of a ship or its parts (speed, weapon settings) to make 
use of the properties (sample implementation with dampening)

this also solves the problem that hundrets of copies of some std::string objects are stored currently

#402