Updated the Makefile to allow easy make-ing of all examples

This diff addresses issue #1 and partially #2. It permits one to simply run
"make" and have all the examples automatically compile. One can also run "make
stencil_name" for the stencil "tb_stencil_name.cpp" to make said stencil.

Running "make check" allows one to run an extra set of additional checks,
though currently these are simply existence check to ensure that the examples
compile properly.

Running "make DEBUG_POCHOIR=1" and "make DEBUG_ICC=1" makes the examples in
debug and icc debug mode, respectively. Similarly, you can run "make check
DEBUG_POCHOIR=1" and "make check DEBUG_ICC=1" to run the test suite on these
examples.