Support custom global mango.local.yaml

[ViliamKopecky]

Having ~/.mango-cli/mango.local.yaml.

Priority of configs would be

mango.local.yaml > ~/.mango-cli/mango.local.yaml > mango.yaml

Reason: I like to develop on local https, but browsersync works on http by default. So at the moment i reuse the same mango.local.yaml with browsersync https config.