Resolve the fixed version number in the Maven POMs

[Zarquan]

At the moment we have a fixed version number in the Maven POMs for the generated code:

Calycopis-schema/codegen/java/client/pom.xml

Line 29 in c023f92

<version>1.0.3-SNAPSHOT</version>

and

Calycopis-schema/codegen/java/spring/pom.xml

Line 35 in c023f92

<version>1.0.3-SNAPSHOT</version>

Ideally we want the POM version to reflect the version number in the OpenAPI specification.

Calycopis-schema/schema/v1.0/execution-broker.yaml

Line 28 in c023f92

version: "1.0"

If we refactor the Java builds to use the POM generated by the code generator, then we can set the version number as a parameter to the generator. Alternatively, we could add a prepare step that starts with a template-pom.xml file, and generates the actual pom.xml file used by the Maven build step.