SBT based code generator (#22)

Eventually I managed to compile it!

Changes are as below:

- When you compile using SBT, it automatically generate the source code from templates. If you just want generated sources, `scaloid:generate` task will do this.

- I wrote event listener extractor based on your implementation. Some listeners are added as a result but they have potential issues mentioned at #24.

- removed `setter` helper because it's rarely used and hard to convert to StringTemplate. Maybe we need something more powerful to replace this.

- Included property setters having `nameClashed`. I'll remove them if it's excluded by intention.

- Some hacks are used for the interoperability between Scala and Java. I tried to keep readability of the source code, but additional discussion or comment might be needed.

- Moved package object file to inside of package directory.