Config loading

[dfornika]

Fixes #25

• Ensure that a default config file is installed when uvp is installed
• Provide more detailed documentation on configuration setup
• Allow users to provide a config file on the command-line using the -c or --config flags
• Allow users to provide the krakendb parameter directly on the command-line using the -k or --krakendb flags
• Allow users to provide the threads parameter directly on the command-line using the -t or --threads flags
• Move config parsing to the uvp executable