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

build_logic/packaging/zip/script.gradle

@@ -0,0 +1,41 @@
+task packageZip_processResources(type: Copy) {
+	dependsOn preparePackaging
+
+	from ('src/packaging/zip') {
+		filesMatching('start.*') {
+			filter(
+				org.apache.tools.ant.filters.ReplaceTokens,
+				tokens: [mainJarFile: project.tasks.jar.archiveFileName.get()]
+			)
+		}
+	}
+	from ('src/main/resource/assets/icons/logo256.original.png') {
+		rename 'logo256.original.png', 'logo.png'
+	}
+	from('LICENSE') {
+		rename 'LICENSE', 'LICENSE.txt'
+	}
+	into 'build/tmp/packaging/workingDir'
+}
+
+task packageZip(type: Zip) {
+	description 'Builds the project and creates a cross-platform ZIP package.'
+	group 'Progressia'
+	
+	dependsOn resolveVersion
+	dependsOn requestCrossPlatformDependencies
+	dependsOn build
+	dependsOn preparePackaging
+	
+	dependsOn packageZip_processResources
+	
+	archiveBaseName = project.name
+	archiveAppendix = 'universal'
+	
+	doFirst {
+		archiveVersion = project.version
+	}
+	
+	from 'build/tmp/packaging/workingDir'
+	destinationDirectory = file('build/packages')
+}