Report config arrays in 1-based way, not 0-based

[yruslan]

Background

When you define a numbered list of sources you use 1-based notation:

pramen.sources.1 = [
  #...
]

But when you use config arrays same sources are reported in logs and errors as 0-based:

pramen.sources = [
  #...
]

Error in source: pramen.sources[0] ....

Feature

Report config arrays in 1-based way, not 0-based for consistency.