make config path/name configurable

[billimek]

As a user of blocky,
I want to specify the path & name of the config file instead of expecting it to be hardcoded to /app/config.yml
So that I can use my own path design for config files

The reason behind this ask is that within kubernetes, leveraging a configMap to define the config file will result in the /app directory being clobbered when mounting the config.yml in that directory meaning that there won't be a blocky binary to run. If we can define the config file to be in a non-shared path, that would be great!

[0xERR0R]

config.yml must be in a working directory. Configurable path would be indeed really useful

[0xERR0R]

Path to config can be specified with optional argument "--config <path_to_config_yml>"