Added Janino to BOM

Hi,

In order to evaluate conditional expressions in configuration files Logback requires [1] Janino to be in the classpath. Since Spring BOM provides preferred version of the Logback...

    <dependency>
      <groupId>ch.qos.logback</groupId>
      <artifactId>logback-classic</artifactId>
    </dependency>

... it will be nice to have the proper version of Janino for that Logback out of the box as well:

    <dependency>
      <groupId>ch.qos.logback</groupId>
      <artifactId>logback-classic</artifactId>
    </dependency>
    <dependency>
      <groupId>org.codehaus.janino</groupId>
      <artifactId>janino</artifactId>
    </dependency>

Cheers.

[1] http://logback.qos.ch/codes.html#ifJanino