KieScanner behavior for already existing KieBases and KieSessions

[tarilabs]

With reference to Drools-usage Google group discussion Ref.
https://groups.google.com/d/topic/drools-usage/XpFlRNjuc9c/discussion

Report below summary for reference.

I think statement is missing to describe
what happens to already existing KieSession and KieBase; from the
current description I would have assumed only "new" stuff gets
up-to-date, but (fortunately!) also some type of already-existing
KieSession and KieBase gets automatically updated.

Current behavior "From this moment on" proved by code actually is:

1- already existing KieBase, generated with getKieBase() : it does get
automatically updated. This is the use case of named KieBase or default
KieBase referenced from kmodule.xml

2- already existing KieBase, generated with newKieBase() : NOT
automatically updated. This is the use case of KieBase created with
"custom" KieBaseConfiguration settings and NOT referencing kmodule.xml

3- any KieBase generated after the KieScanner updated, with either
getKieBase() or newKieBase() : directly the newer version, simple case,
indeed as already mentioned in the documentation.

Behavior for already existing KieSession depends on the underlying
KieBase, so it make reference to the cases described here-above.
To be fully explicit, when already existing KieSession was generated
directly from KieContainer.newKieSession() is case #1 because it implies
the default KieBase from kmodule.xml.

[kie-ci]

Can one of the admins verify this PR? Comment with 'ok to test' to start the build.

[psiroky]

@mariofusco could you please take a look?