Replaced log4j with slf4j.

This removes the dependency on log4j and allows the user to use whatever logging framework they want, e.g. log4j, JUL, JCL, logback, etc
Replaced ant with maven.

Removed the build.xml since maintaining 2 build processes is a waste of time
Added *.iml to ignore.

Prevents Intellij project files being committed.
Added slf4j-simple to test scope.

For the sake of a couple of simple unit tests it's all that is needed to get the logging output.
Updated tests to use junit4 annotations
Updated test to get resources via relative classpath instead of a hardcoded path
Added support for modifying tags

Can now perform the following actions on tags
* Add
* Edit
* Delete
Version bump
Changed add tags to support multiple tags in one update
Merged latest from rushimusmaximus/exiftool
added IDEA workspace files to gitignore list
merged latest from mattshep2000/exiftool