Add default value

[sheb-gregor]

Add new type noble.Value with support of default values.

New syntax will use || as a separator.

Here is an example:

db: "env:MY_APP_DB||test_database"

db =  "env:MY_APP_DB||test_database"

Expected behavior:

Try to retrieve the value by key from the environment (or another supported driver). If the retrieved value is empty, use the default value.