Add FUSE and IOFSL IOStore support

After FUSEIOStore is added, any file system who has FUSE export
could be used as PLFS backends easily.

IOFSL IOStore is an example of that which supports the IOFSL
backends.
List the source files for tools to avoid cmake error.

cmake 2.8.10 will complain about linker language as following:
  CMake can not determine linker language for target:dcon

So I list the full pathname of the source file so that cmake
could know whether it is a C file or a C++ file.
Add support for building test tools.

Unit test tools are useful for testing the correctness of PLFS.
So build them when cppunit is found.
Merge pull request #214 from zhang-jingwang/2.4dev

2.4dev add new IOStore for FUSE and IOFSL.