gh-159 Switch to SBT for better cross-compiled jar/module generation

* Package builds a jar and module.
* Cross compilation packaging generates modules for all Scala versions.
* copyMod task ported over to SBT.
* Added mod zip file as extra artifact generated which installs
locally via 'publishM2' task.
* Adjust release script to use SBT.
* Remove old gradle files.

Conflicts:
	.gitignore
	gradle.properties
Add ability to release of a different branch
gh-159 First SBT release fixes: substitute version in correct files

* Add publishM2 so that it also publishes locally. This can be handy
for testing Vert.x locally before doing final release.
gh-159 Correct SBT commands to use to release
gh-159 Remove duplicate <description/> from generated pom file
gh-159 Module registry needs `mod` classified in ZIP file's name
gh-171 Fix named parameter used when binding variables in interpreter

* Upgrade to Scala 2.11.2 for cross compilation.
* Fix error reporting in interpreter test.
gh-159 SBT build instructions and IDE integration documentation added
gh-172 Fix module location for compilation on Windows

* Using toExternalForm on URL produces a UNIX-style path which does
not work fine on Windows machines. Instead, create a File with the
URL's URI and get absolute path for it, which produces a plattform
dependant path.