[Scala][Akka] Ensure identifiers get sanitized & model names have the same formatting

[paul-english]

…me formatting

PR checklist

• Read the contribution guidelines.
• Ran the shell/batch script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh and ./bin/security/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates)
• Filed the PR against the correct branch: master for non-breaking changes and 2.3.0 branch for breaking (non-backward compatible) changes.

Description of the PR

(details of the change, additional tests that have been done, reference to the issue for tracking, etc)

[paul-english]

I'm not sure why the travis test fails, maybe some upstream issue.

One thing on this PR, I re-ran bin/akka-scala-petstore.sh and it reverted pom.xml changes found in 2da2a26 (Note, I didn't add that file to this PR)

@wing328 Can you comment on what that pom.xml change was, and if we need to update the shell script or something else for this.

[paul-english]

Also there's no coverage for the specific case we saw that required the override for toModelName. We have a subclass typing patter where we end up with definitions of the form Customer.Id, when the period is in there it generated an invalid case class in scala code, so by running the model name through the format identifier method it cleans that period out.

[ePaul]

See #5094 for the pom update issue.

[wing328]

@log0ymxm thanks for the PR, which looks good to me.

Eventually, we want to consolidate scala, async-scala and akka-scala into a single Scala API client generator. @clasnake has begun the effort with #5115. Please review the change when you've time.