Implement logging with Log4j2 for aws-scala-sbt

[NomadBlacky]

What did you implement:

Closes #XXXXX

How did you implement it:

• Implemented logging that recommended by AWS.

How can we verify it:

$ sls create -t aws-scala-sbt -p sls-scala
$ cd sls-scala
$ sbt assembly
$ sls deploy
$ sls invoke -f hello
$ sls logs -f hello # Please check to log from the function.

Todos:

• Write tests
• Write documentation
• Fix linting errors
• Make sure code coverage hasn't dropped
• Provide verification config / commands / resources
• Enable "Allow edits from maintainers" for this PR
• Update the messages below

Is this ready for review?: YES
Is it a breaking change?: NO

[NomadBlacky]

A sbt-plugin has been released that merges Log4j2Plugins.dat.

• https://github.com/idio/sbt-assembly-log4j2

However, it doesn't support sbt 1.x.
I released a fork that supports sbt 1.x.

• https://github.com/NomadBlacky/sbt-assembly-log4j2

[pmuens]

Just tested this and it works fine. Thanks @NomadBlacky! 👍

LGTM