Migration to a maven build:

Hello,

Here is a pull request to move to a maven build for your project.
I use it in a personal project and having a maven build helps me and maybe others (you can publish it on a central repository).
By the way with a maven build you can configure a Travis CI job to compile on code change update.

Details
- move sources to src/main/java
- move InternetCodepages.txt and PropertyNames.txt to src/main/resources
- add a simple pom.xml: I've choose "com.pff" for groupId and "java-libpst" for artifactId but let me know if you'd like something else
- update .gitignore to ignore target directory

Thanks,

Franck