upmc: Updates for building C modules w/base UPM

Test commit for building C UPM modules.

    * Added C include directory
    * Added C utilities directory
    * Rename C++ upm.h -> upm.hpp to make room for C upm.h
    * Added upm_mixed_module_init function to src/CMakeLists.txt.  This
      function takes filesnames similar to upm_module_init and does a
      bit of processing before calling upm_module_init.
    * Added c example directory.  Changed c++ example names.
    * Added dfrph implemention for testing (C++ wraps C).  Added mraa
      to .pc requires for dfrph.  Tested against stand-alone project.
      Added dfrph c example.
    * Update implemention of pkg-config file generation.
    * Added two cmake cache variables: BUILDCPP and BUILDFTI
    * Removed src from swig_add_module calls, added libname to
      swig_link_libraries calls.  Shrinks swig'ed binaries by ~13%.
    * Added install target in upm/CMakeLists.txt to install C header,
      directory.  Is this where we want this?
    * C FTI header directory is include/fti

Signed-off-by: Noel Eck <noel.eck@intel.com>

docs/documentation.md

@@ -66,7 +66,7 @@ Here's an example (disregard the "@verbatim" tags in your actual code):
 - `<component-kit>` Specifies if the sensor is part of a kit. *Optional*
 
 Existing groups that can be used for the manufacturer, connection, category and
-kit tags are found in the src/upm.h file.
+kit tags are found in the src/upm.hpp file.
 
 Optionally, a small representative image can be placed in the "docs/images"
 subfolder and linked with the "@image" tag.