Initial Litecoin support

Added altcoinj library as Maven dependency.

Added new Litecoin subclass of Bitcoiny,
with mainnet and testnet ElectrumX server lists.

Added litecoinNet settings variable and getter.

Added LitecoinTests.
Most tests work but testFindHtclSecret()
needs a redeemed HTLC on chain (not yet done).

Added litecoinNet to some test settings files
in resources.

Added Litecoin BuildHTLC, Refund test apps.

Added SendLTC app as Electrum-LTC seems a bit flaky?

So far managed to build HTLC P2SH, fund it and then
refund it!

---

As Bitcoin and Litecoin are both subclasses of Bitcoiny,
could unify some test apps with added Bitcoin/Litecoin
switch as first arg?

pom.xml

@@ -6,7 +6,8 @@
 	<version>1.3.5</version>
 	<packaging>jar</packaging>
 	<properties>
-		<bitcoinj.version>0.15.5</bitcoinj.version>
+		<altcoinj.version>bf9fb80</altcoinj.version>
+		<bitcoinj.version>0.15.6</bitcoinj.version>
 		<bouncycastle.version>1.64</bouncycastle.version>
 		<build.timestamp>${maven.build.timestamp}</build.timestamp>
 		<ciyam-at.version>1.3.7</ciyam-at.version>
@@ -375,6 +376,11 @@
 			<name>project</name>
 			<url>file:${project.basedir}/lib</url>
 		</repository>
+		<!-- jitpack for build-on-demand of altcoinj -->
+		<repository>
+			<id>jitpack.io</id>
+			<url>https://jitpack.io</url>
+		</repository>
 	</repositories>
 	<dependencies>
 		<!-- https://mvnrepository.com/artifact/org.codehaus.mojo/build-helper-maven-plugin -->
@@ -415,6 +421,12 @@
 			<artifactId>bitcoinj-core</artifactId>
 			<version>${bitcoinj.version}</version>
 		</dependency>
+		<!-- For Litecoin, etc. support, requires bitcoinj -->
+		<dependency>
+			<groupId>com.github.jjos2372</groupId>
+			<artifactId>altcoinj</artifactId>
+			<version>${altcoinj.version}</version>
+		</dependency>
 		<!-- Utilities -->
 		<dependency>
 			<groupId>com.googlecode.json-simple</groupId>