Rewrote build script, improved packaging

- Renamed :packageWindows to :packageNsis
- ImageMagick now required for :packageNsis
- Packaging output is now in build/packages
- Rewrote build script
  - Packaging logic and LWJGL dependencies now in separate files
  - Packaging logic now implemented with Gradle, not Bash scripts
    - Cross-platform?
- Added :packageZip
  - Universal ZIP with start scripts
- Changed version detection logic
  - Tags of ancestor commits are now considered
  - Only tags with format vMAJOR.MINOR.PATCH[-SUFFIX] are considered
  - If the tag's commit isn't HEAD, PATCH is incremented
  - When version detection fails, dummy version is 999.0.0-<buildID or date>
- LWJGL target platforms can be overridden with forceTargets project property

src/packaging/deb/DEBIAN/control

@@ -0,0 +1,8 @@
+Package: progressia
+Version: ${version}
+Section: custom
+Priority: optional
+Architecture: all
+Maintainer: Javapony <kvadropups@gmail.com>
+Depends: java8-runtime
+Description: Progressia - a 3D sandbox survival game