TEIIDDES-1763: Add source jar support to modeshape plugin

* Adds downloading of modeshape source jars to the libsrc directory to
  allow for source display in eclipse

* .classpath
 * Plumbing for the display of source for each downloaded library

* pom.xml
 * Profile adds source download and copying ability but must be called
   explicitly so should not interfere with binary builds

* .gitignore
 * Ignores libsrc directory
TEIIDDES-1768: Replace exec calls to mvn with common utility macro

* Imports the mvn macro from the common build script. This macro tries to
  execute the correct command for the OS that the script is being run on

* scripts/build-common.xml
 * Defines the mvn macro for platform dependent execution