Issue #7: Use SLF4J instead of JUL.

- Update build.gradle with SLF4J and Logback dependencies.
- Clean up depdendencies closure and use extension properties for the
  versions of dependencies.
- Clean up descriptions of start and stop tasks.
- Replace usage of System.err and other logging methods with SLF4J.
Merge branch 'master' of https://github.com/ReadyTalk/revori into slf4j

Conflicts:
	server/build.gradle
	server/src/main/java/com/readytalk/revori/server/SQLServer.java
Issue #7: Address feedback from code review.

- Wrapped potentially expensive calls to Util.toString() with an
  isDebugEnabled() check.
- Updated log levels of a couple of logging statements.
Merge pull request #7 from dougborg/slf4j

Use SLF4J instead of java.util.Logging