Improve docs on configuring mail notifiers

      <configuration>
        <from-mailbox></from-mailbox>
        <from-name></from-name>
        <timestamp-format>EEE d MMM yyyy HH:mm:ss Z</timestamp-format>        <!-- Customizable mail subject.  Use any combination of literal text, or
 state, project, or build attributes.          Examples:
            "[continuum] BUILD ${state}: ${project.groupId} ${project.name}"
              results in "[continuum] BUILD SUCCESSFUL: foo.bar Hello World"
            "[continuum] BUILD ${state}: ${project.name} ${project.scmTag}"
              results in "[continuum] BUILD SUCCESSFULL: Hello World Branch001"

            "[continuum] BUILD ${state}: ${project.name} ${project.version}"
              results in "[continuum] BUILD SUCCESSFUL: Hello World 2.1-SNAPSHOT
"

            "[continuum] BUILD ${state}: ${project.name} ${build.durationTime}"
              results in "[continuum] BUILD SUCCESSFUL: Hello World 2 sec"

            "[continuum] BUILD ${state}: ${project.name}, Build Def - ${build.buildDefinition.description}"
              results in "[continuum] BUILD SUCCESSFUL: Hello World, Build Def - Nightly Test Build"
         -->
        <subject-format>[continuum] BUILD ${state}: ${project.projectGroup.name} - ${project.name} - ${build.buildDefinition.description}</subject-format>
        <includeBuildResult>true</includeBuildResult>
        <includeBuildSummary>true</includeBuildSummary>
        <includeTestSummary>true</includeTestSummary>
        <includeOutput>false</includeOutput>
        <alwaysSend>false</alwaysSend>
      </configuration>
    </component>