[WIP ] rework configuration and documentation => better default

[wiibaa]

Reworked the plugin to achieve expected behaviour described in #1 => empty config create one clone.
But keep backward compatibility
Improved the documentation

@purbon or @jsvd I would need some guidance on correctly testing the yielded event in the spec if you extra time for review

[elasticsearch-release]

Jenkins standing by to test this. If you aren't a maintainer, you can ignore this comment. Someone with commit access, please review this and clear it for Jenkins to run; then say 'jenkins, test it'.

[jsvd]

I've been thinking about this, what if instead of having single/multiple setting with :mode, set instead a default for :clones ? For example:

config :clones, :validate => :array, :default => ["clone"]

this way the default behaviour of clone {} is the creation of 1 clone, and the clone will have type => clone

[anitakrueger]

Any chance of merging this? I've just tried to use the clone filter with the current documentation and couldn't make it work.
I came here because I found #1

[jsvd]

hi @anitakrueger, newer versions of the clone filter require clones to be set, and warn if the array is empty https://www.elastic.co/guide/en/logstash/7.2/plugins-filters-clone.html#plugins-filters-clone-clones

[anitakrueger]

@jsvd I saw this in the documentation, yes. Unfortunately there is no example present for the clones configuration option. However for the common options there are lots of examples and none of them include clones. This is confusing.
In addition to that the documentation says that the value type for clones is array, but it does not list the possible options. How is a user supposed to know to set it to clone?