Avoid code dupplication for spring 3 and spring 4 support.

[FlorianGWE]

At the moment spring 3 and spring 4 support are done with code duplication. Spring 3 and Spring 4 have compile incompatible changes:

• TestContext in Spring 3 is a class
• TestContext in Spring 4 is a inteface

Following projects for spring are effected:

• flyway-spring-test
• flyway-spring3-test
• flyway-spring4-test

Following project for dbunit are effected:

• flyway-dbunit-test
• flyway-dbnit-spring3-test
• flyway-dbunit-spring4-test

It should be tested if it is possible to use the source files from one module to use it in spring3 or spring4 and compile it against the correct Spring version again.

[FlorianGWE]

Now we use maven-dependency-plugin to extract source code from flyway-spring-test in project

• flyway-spring3-test
• flyway-spring4-test and compile it with the correct dependency

=> no code duplication

Now we use maven-dependency-plugin to extract source code from flyway-dbunit-test in project

• flyway-dbunit-spring3-test
• flyway-dbunit-spring4-test and compile it with the correct dependency

=> no code duplication