Replaced printlns with logging, moved delete() to FileUtils.

components/net/sf/briar/db/DatabaseComponentImpl.java

components/net/sf/briar/db/H2Database.java

components/net/sf/briar/db/JdbcDatabase.java

...nents/net/sf/briar/db/ReadWriteLockDatabaseComponent.java

...onents/net/sf/briar/db/SynchronizedDatabaseComponent.java

components/net/sf/briar/protocol/BatchImpl.java

test/net/sf/briar/util/FileUtilsTest.java

util/net/sf/briar/util/FileUtils.java