Initial stab at migrating to HSQLDB for Qora gen2

Most SQL tables defined but only payment transactions actually implemented.
Maven support added.

Some code imported from 'old' Qora:

RIPEMD160 renamed as BrokenMD160 and deprecated.
whispersystem's Ed25519 implementation (to be replaced with bouncycastle).
Basic Account/PublicKeyAccount/PrivateKeyAccount code.
Some utils like Base58 and Pair.

To use:

Use maven to fetch dependencies.
Build project.
Fire up an old-gen Qora node.
Run src/test/update.java as a JUnit test to build DB structure.
Run src/test/migrate.java as a JUnit test to migrate old Qora blocks to DB.

You should now be able to run src/test/load.java and src/test/save.java
as JUnit tests demonstrating loading/saving Transactions from/to database.

This commit done while halfway through adding Block support!

.gitignore

@@ -0,0 +1,3 @@
+/db*
+/bin/
+/target/