Networking and repository

Some pom.xml changes to reduce maven-shade-plugin conflicting classes warnings.

Repository now supports SAVEPOINT and ROLLBACK TO SAVEPOINT.
HSQLDB concurrency/transaction model changed from LOCKS to MVCC to help with
 transaction deadlocks/rollbacks.

More XXXs and TODOs added to Block.java for investigation/fix/improvements.
Also used new repository SAVEPOINT feature when validating transactions
 instead of rolling back entire transaction. This fixes problem during
 synchronization where the rollback would undo previously synchronized,
 but not yet committed, blocks!

Transactions orphaned by Block.orphan ARE now added to unconfirmed pile,
 unlike before.

Concurrent lock now prevents simultaneous block generation and synchronization,
 including synchronization via multiple peers.

Lots of new networking code: peer lists, block signatures, blocks,
 blockchain synchronization.

PEERS_V2 message now supports hostnames, IPv6 and port numbers.

Fixed bug with block serialization for transport over network.

pom.xml

@@ -385,6 +385,12 @@
 			<groupId>org.glassfish.jersey.inject</groupId>
 			<artifactId>jersey-hk2</artifactId>
 			<version>${jersey.version}</version>
+			<exclusions>
+				<exclusion><!-- exclude javax.inject-1.jar because other jersey modules include javax.inject v2+ -->
+					<groupId>javax.inject</groupId>
+					<artifactId>javax.inject</artifactId>
+				</exclusion>
+			</exclusions>
 		</dependency>
 		<dependency>
 			<groupId>org.glassfish.jersey.media</groupId>
@@ -406,6 +412,12 @@
 			<groupId>io.swagger.core.v3</groupId>
 			<artifactId>swagger-jaxrs2-servlet-initializer</artifactId>
 			<version>${swagger-api.version}</version>
+			<exclusions>
+				<exclusion><!-- excluded because included in swagger-jaxrs2-servlet-initializer -->
+					<groupId>io.swagger.core.v3</groupId>
+					<artifactId>swagger-integration</artifactId>
+				</exclusion>
+			</exclusions>
 		</dependency>
 		<dependency>
 			<groupId>org.webjars</groupId>