Added class Application and completed MesonBuilder
Added class Application and completed MesonBuilder

Creates a one library with 1 function and a test application
that calls that function. I.e. the following works:

 $ ./gen_src.py test 1 1
 $ cd test
 $ mkdir build
 $ cd build
 $ meson ..
 $ ninja
 $ ./app/testapp/testapp

winksaville/gen_srcs