[NCL-3310] Allow override config location using env variable
[NCL-3310] Allow override config location using env variable

When PNC_CONFIG_LOCATION environment variable is set, this is
folder where pnc-cli will look for its configuration. Otherwise
it looks into ~/.config/pnc-cli/.

project-ncl/pnc-cli,janinko/pnc-cli,janinko/pnc-cli,project-ncl/pnc-cli,thauser/pnc-cli,project-ncl/pnc-cli,thauser/pnc-cli,janinko/pnc-cli,thauser/pnc-cli