Dynamic runtime and error reporting

[eldoy]

Should we write a more dynamic runtime? How do we map code line numbers to errors? At the moment it's a bit hard to know where an error originated. It would be nice to have something like:

Error on line 1: @db: $result in file 'tester.yml'
Stacktrace:
set $result, {hello: 1}
# See other issue about stack trace

The runtime could break the YAML into separate sections, which are interpreted on the fly. This way we don't need internal IDs (#cuid) since there would be no duplicates.

Should we use a custom parser? It's a pain to re-implement a YAML parser...