Support for selecting by DataType in the SearchBuilder and ListBuilder

Thanks to @msomhorst for implementing the following:

• support for selecting by DataType in the SearchBuilder and ListBuilder
• update the XSD with latest openapi content

Besides that:

• the README has been updated to include a link to an example on
  how to configure JCenter as repository in a Maven project

API now usable for Java projects

So far the API was only used with Groovy projects. As Groovy marks protected classes public, SearchBuilder and ListBuilder were perfectly fine to use. But not in Java projects.

Now these classes have been made public, for use with Java projects.

bol.com OpenAPI v4 java client

Provides an easy way to communicate with the bol.com OpenAPI v4.

The client is what you want to use as dependency of your project. The client provides the easy way of communicating. See client README.md on how to use it.

To get the bol.com OpenAPI client binaries, add the JCenter repository (https://bintray.com/bintray/jcenter) and the following dependency:

• Maven

  <dependency>
      <groupId>com.bol.openapi</groupId>
      <artifactId>openapi-java-client</artifactId>
      <version>4.0.0</version>
  </dependency>

• Gradle

  repositories {
      jcenter()
  }
  dependencies {
      compile 'com.bol.openapi:openapi-java-client:4.0.0'
  }
  

Requirements

• Java 7+
• A bol.com developer key (which you can request at https://developers.bol.com)

OpenAPI limitations

(based on the bol.com OpenAPI documentation)

• Max. 2000 requests per 60 minutes
• Session lives for 20 minutes without activity