Keppler configuration file support

[lafusew]

Use of a json config file instead of command line parameters as asked in #66

Features & Behavior

Added --config param for specifying the JSON config file path.

As the config param is defaulted to .kepplerrc it silently try to read a config file, if found: read the configuration.

Configuration file should be a JSON with key-values following documented parameters rules. e.g:

{
  "name": "My project",
  "host": "localhost",
  "port": "8080",
  "open": true,
  "debug": 1
}