Single config

According to #243 (closed), Vadere should read all configuration parameters from a single file.

Provide following functionality:

• Use OS-specific location to store config file (home directory preferred).
• Write default config file if no config file exists or errors occur while reading existing config file.
• Add flag --config-file <path/to/file> to all(!) Vadere applications (i.e., GUI, Console, PostVis, ...).

Furthermore, remove old config code. I.e., the preferences.put(...) calls and the corresponding ApplicationWriter.savePreferences() calls.