Changed project's structure to a Maven project and splitted it into a core project and a webapp example to show how it works

Dear Don Park,

First of all, I'd like to say thank you for making identicon open source and making developer's life easier when it comes to generating user's avatar and many others purposes.

Here are a few changes I've made to your code and I hope you accept my pull request:

+ Type of project

    * I've changed the project to a Maven project so we could have a platform independent modules ( core, web or even mobile modules in the future)
    * I've created a web application module that uses Tomcat plugin so that user doesn't need to create a project to test identicon

+ Cache framework

    * When I was changing its project type to maven I realised that whirlycott framework isn't working project due to a buggy version on repo.central which seems like to be missing a locale bundle. So I took the liberty to change  whirlycott to cache2k which is way faster and keep that same methods in MemoryIdenticonCache class.

Sincerely 

Paulo Miguel Almeida