[JENKINS-24076] Add a configuration option for stable build comparison

Add a configuration option for Cppcheck to compare results against a stable build rather than the last
build.
stableBuild would be stored to build.xml together with all non-transient fields now. This data file should contain only data from the particular build, stableBuild is global configuration flag.

    <org.jenkinsci.plugins.cppcheck.CppcheckBuildAction>
      <owner class="build" reference="../../.."/>
      <result>
        <owner class="build" reference="../../../.."/>
        <statistics>
          <errorCount>0</errorCount>
          <warningCount>1</warningCount>
          <styleCount>22</styleCount>
          <performanceCount>2</performanceCount>
          <informationCount>1</informationCount>
          <noCategoryCount>0</noCategoryCount>
          <portabilityCount>0</portabilityCount>
          <versions>
            <string>1.61</string>
          </versions>
        </statistics>
        <stableBuild>false</stableBuild>    <!-- *** HERE *** -->
      </result>
      <healthReportPercentage>-1</healthReportPercentage>
    </org.jenkinsci.plugins.cppcheck.CppcheckBuildAction>