Added a way to configure the tool with .ini like configure file

Important points:
- Configure file can be specified as a command line parameter
- If not specified configure file would be ~/.config/yatt/.yattconfig
- If not specified configure is going to be generated when you run the
  tool for the first time.
- Sqlite db file is going to be there in ~/.config/yatt/ by default
  unless you set the value of 'data_dir' to be something else.
- Config files are in .ini format parsed by ConfigParser
- The values of config keys are json formatted to support lists.