EHN: Add subprojects dependencies visualization support.

 * Add getsubprojectdependencies php components to query the database
   and return subproject dependency in json format.
 * Add d3.dependencyedgebundling javascript component and corresponding
   css. This component support adaptive automated sizing.
 * Add viewSubprojectDependenciesGraph php and corresponding xsl.
Merge pull request #1 from jasonli2000/dep-visualization

EHN: Add subprojects dependencies visualization support.