updates for jhipster 6.x compatibility

[funder7]

In order to use the blueprint I've manually done the fix reported in issue #1;

The generated payment.jh is throwing an error due to bidirectional relationship not allowed. I updated the file from this:

// ...
relationship ManyToOne{
	Payment{user} to User{payment}
}

to this

// ...
relationship ManyToOne{
	Payment{user} to User
}

Probably the other end of the relationship will be missing (in case I will add it manually later).

Then, package.json:

  "dependencies": {
    "chalk": "^2.4.1",
    "fs": "0.0.1-security",
    "generator-jhipster": "^6.10.1", <------
    "lodash": "^4.17.19",
    "mkdirp": "0.5.1",
    "semver": "5.3.0",
    "shelljs": "^0.8.4",
    "yeoman-generator": "^4.11.0"
  },

And finally in the index.js

            // Maven + AngularX
            if (this.buildTool === 'maven') {
                jhipsterUtils.rewriteFile({
                    file: 'pom.xml',
                    needle: 'jhipster-needle-maven-add-dependency',
                    splicable: [`<dependency>
                <groupId>com.stripe</groupId>
                <artifactId>stripe-java</artifactId>
                <version>19.35.0</version>    // <--------------------------------------------
            </dependency>`]
                }, this);

I hope that the update from v7 to v19 is not introducing any breaking change in the API. Well, we will figure it out. : )

Sorry I can't open a PR, btw is this project still followed?