feat: add external file for other configs

[eminaktas]

This PR adds new optional field to pass templates as file for all other configuration in values.yaml

Example:

config/
├── krakend.tmpl
├── partials
│   ├── input_headers.tmpl
│   └── rate_limit_backend.tmpl
├── settings
│   └── dev
│       ├── backends.json
│       ├── endpoints.json
│       └── service.json
└── templates
    └── endpoints.tmpl

configFileSource: "config/krakend.tmpl"
partialsDirSource: "config/partials/**.tmpl"
settingsDirSource: "config/settings/dev/**.json"
templatesDirSource: "config/templates/**.tmpl"

[JAORMX]

Thanks for working on this!