Ordered Array when parsing configuration values

[ph]

Let's say we want to create a mapping table to replace values from an integer to a string, this is currently not possible with the current config type casting.

Example:

potato:
  1: "abc"
  2: "oko"
  50: "noo"

When loaded from ucfg, the map get converted into an slice.

potato:
  - "abc"
  - "oko"
  - "noo"

Even if you escape the key as a string, ucfg will try to convert the value to an integer and succeed.

potato:
  "1": "abc"
  "2": "oko"
  "50": "noo"

potato:
  - "abc"
  - "oko"
  - "noo"

After discussing with @urso on zoom we would like to support the following use case to reduce the size of the configuration and the verbosity of usings keys in the yaml.

config:
  2: v1
  5: v2

config:
  - a
  - b

cfg *common.Config // table = map + array
var m map[string]string
var a []string

cfg.Unpack(&m) // map[2: v1, 5: v2]
cfg.Unpack(&a) // [a, b]

cfg.Unpack(&m) // map[2: v1, 5: v2, 0: a, 1: b]
cfg.Unpack(&a) // [a, b]

[ph]

@urso updated with our example from our talk.