Fix PlayEbean configuration loading for sub projects (#209)

[LeComptoirDesPharmacies]

The goal of this PR is to modify the way Configuration was moved to Config in order to keep the capability to build sub projects with PlayEbean inside.

See #209 for more details.

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[felipebonezi]

@LeComptoirDesPharmacies hi, this PR is very important to our community.

Did you Test with multiple sbt projects?
BTW, can you explain why just change to Scala Configuration class fix it?

[LeComptoirDesPharmacies]

Hi @felipebonezi,

On our side we built a fork of 6.0.0 with content of this PR and we are running it on our production server but we would like to use the official build to benefit from future enhancements.

We created this minimal reproducer that you can clone/run to see the error/behavior. (Just go to localhost:9000)
https://github.com/LeComptoirDesPharmacies/IssuePlayMultiProject

Here is a branch of the same project using old "play-ebean 4.1.4" which was working.
https://github.com/LeComptoirDesPharmacies/IssuePlayMultiProject/tree/workingIn2.6

We did not test this on other SBT projects but do not hesitate to tell us If you have any project in mind where we could test it.

Explanation of the problem:
In versions < Play 2.7, "Configuration" class was reworked with a "Config" interface.
This PR (https://github.com/playframework/play-ebean/pull/157/files) updated the ModelsConfigLoader.java to reflect this new naming.

As you can see, it does not only rename "Configuration -> Config" but it also use env.classLoader() instead of env.
env.classLoader() is the exact same meaning as using the method input parameter classLoader.
In this context, the following lines of code and comment are circumvented, creating error when conf file does not exists.
// Using TEST mode is the only way to load configuration without failing if application.conf doesn't exist Environment env = new Environment(new File("."), classLoader, Mode.TEST);

I think that the author does that because "ConfigFactory" does not have any method with signature capable to "load" "play.Environment" class.

Solution of this PR :
The tips here was to move from Java Environment to Scala one in order to get the good "Configuration.load" signature available.
Then, when calling the "EbeanParsedConfig.parseFromConfig" method, we are using config.underlying to retrieve the Java instance from Scala type as this method require it.

Yours faithfully,
LCDP

[jmswenski]

Tested changes out with our app. LGTM.