Change SnakeYAML dependency to snakeyaml-engine

[dstepanov]

Issue description

SnakeYAML snakeyaml-engine implements spec 1.2 and removed Java Bean deserialization

[gijsleussink]

Using 'org.snakeyaml:snakeyaml-engine:2.10', @EachProperty doesn't seem to work properly.

Configuration requires entries under the prefix …

@EachProperty("a.b.c") and YAML config of the form:

a.b:
  c:
    - d
    - e