Revision 700

A few changes in the build mechanism and the file structure so scons can build release tar files:

  * paso/src/Solver has been moved to paso/src 
  * all test_.py are now run_.py files and are assumed to be passing python tests. they can run by 
    scons py_tests and are part of the release test set
  * escript/py_src/test_ are moved to escript/test/python and are installed in to the build directory 
    (rather then the PYTHONPATH).
  * all py files in test/python which don't start with run_ or test_ are now 'local_py_tests'. they are installed i
    by not run automatically.
  * CppUnitTest is now treated as a escript module (against previous decisions).
  * scons realse builds nor tar/zip files with relvant source code (src and tests in seperate files)

the python tests don't pass yet due to path problems.