Add docs for Flyway Pro and Enterprise Edition usage

[axelfontaine]

The only two changes that are needed are:

Adding an S3 resolvers in project/project/plugin.sbt

addSbtPlugin("com.frugalmechanic" % "fm-sbt-s3-resolver" % "0.14.0")

Excluding the Community Edition flyway-core artifact in project/plugin.sbt and replacing it with the desired edition which will be downloaded from our private repo:

Pro:

s3CredentialsProvider := { (bucket: String) =>
  new com.amazonaws.auth.AWSStaticCredentialsProvider(new com.amazonaws.auth.BasicAWSCredentials("your-flyway-pro-user", "your-flyway-pro-password"))
}
resolvers += "Flyway Repo" at "s3://flyway-repo/release"
addSbtPlugin("io.github.davidmweber" % "flyway-sbt" % "5.0.0-RC2" exclude("org.flywaydb", "flyway-core"))
libraryDependencies += "org.flywaydb.pro" % "flyway-core" % "5.0.7"

Enterprise:

s3CredentialsProvider := { (bucket: String) =>
  new com.amazonaws.auth.AWSStaticCredentialsProvider(new com.amazonaws.auth.BasicAWSCredentials("your-flyway-enterprise-user", "your-flyway-enterprise-password"))
}
resolvers += "Flyway Repo" at "s3://flyway-repo/release"
addSbtPlugin("io.github.davidmweber" % "flyway-sbt" % "5.0.0-RC2" exclude("org.flywaydb", "flyway-core"))
libraryDependencies += "org.flywaydb.enterprise" % "flyway-core" % "5.0.7"

Please include this in the README and the manual.