Support generation of native installer binaries

Use `./gradlew run` to build and run Bitsquare directly.

Use `./gradlew shadowJar` to generate a portable, executable jar.

Use `./gradlew packageNative` to generate an installer binary specific
to the platform you are running on.

In the case of Windows, it is necessary to copy the two .dll files in
the `package/` directory to the directory where Bitsquare.exe is
ultimately installed.

Resolves #243

build.gradle

@@ -1,3 +1,9 @@
+import org.apache.tools.ant.taskdefs.condition.Os
+
+plugins {
+  id "com.github.johnrengelman.shadow" version "1.1.2"
+}
+
 apply plugin: 'java'
 apply plugin: 'eclipse'
 apply plugin: 'application'
@@ -41,4 +47,17 @@ dependencies {
     testCompile 'org.mockito:mockito-all:1.9.5'
 }
 
+task packageNative(type:Exec, dependsOn:shadowJar) {
+    if (Os.isFamily(Os.FAMILY_MAC))
+        executable "${project.rootDir}/package/mac.sh"
+    else if (Os.isFamily(Os.FAMILY_UNIX))
+        executable "${project.rootDir}/package/linux.sh"
+    else if (Os.isFamily(Os.FAMILY_WINDOWS))
+        executable "${project.rootDir}/package/windows.bat"
+    else
+        throw new GradleException("Unsupported OS: " + System.properties['os.name'])
+
+    args project.version, shadowJar.archivePath, mainClassName
+}
+
 wrapper.gradleVersion = '2.1'

package/linux.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+
+set -e
+
+version=$1
+jar=$2
+mainClass=$3
+
+javapackager -deploy \
+    -BappVersion=$version \
+    -Bcategory=Finance \
+    -BlicenseType=GPLv3 \
+    -Bemail=info@bitsquare.io \
+    -native deb \
+    -name Bitsquare \
+    -title Bitsquare \
+    -vendor Bitsquare \
+    -outdir build \
+    -appclass $mainClass \
+    -srcfiles $jar \
+    -outfile Bitsquare
+
+# -Bicon=client/icons/icon.png \

package/mac.sh

@@ -0,0 +1,24 @@
+#!/bin/bash
+
+set -e
+
+version=$1
+jar=$2
+mainClass=$3
+
+javapackager \
+    -deploy \
+    -BappVersion=$version \
+    -Bmac.CFBundleIdentifier=bitsquare \
+    -Bmac.CFBundleName=Bitsquare \
+    -Bruntime="$JAVA_HOME/../../" \
+    -native dmg \
+    -name Bitsquare \
+    -title Bitsquare \
+    -vendor Bitsquare \
+    -outdir build \
+    -srcfiles $jar \
+    -appclass $mainClass \
+    -outfile Bitsquare
+
+#-Bicon=client/icons/mac.icns \

package/windows.bat

@@ -0,0 +1 @@
+C:\Progra~1\Java\jdk1.8.0_20\bin\javapackager.exe -deploy -BappVersion=0.1.0 -native exe -name Bitsquare -title Bitsquare -vendor Bitsquare -outdir build -appclass io.bitsquare.BitSquare -srcfiles .\build\libs\bitsquare-0.1.0-SNAPSHOT-all.jar -outfile Bitsquare -Bruntime="c:\Program Files\Java\jdk1.8.0_20\jre"