zfm20: Use mraa::Uart instead of tty

Updated the ZFM20 class to use UART functionality provided through the
mraa::Uart class instead of using the UART directly.

    * Switch to mraa::Uart
    * Added raw uart string constructor, closes #621
    * Updated examples
    * Added a common.i to minimize interface duplication
    * Removed pointers from C++ functions where references are
      preferable
    * Removed dependency on termios
    * Added typedefs to handle pass-by-reference
    * Removed flushes
    * Removed code after throws

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

examples/c++/zfm20.cxx

@@ -38,7 +38,7 @@ main(int argc, char** argv)
     upm::ZFM20 fp(0);
 
     // make sure port is initialized properly.  57600 baud is the default.
-    if (!fp.setupTty(B57600)) {
+    if (!fp.setupTty(57600)) {
         cerr << "Failed to setup tty port parameters" << endl;
         return 1;
     }
@@ -83,7 +83,7 @@ main(int argc, char** argv)
 
     // we search for a print matching slot 1, where we shored our last
     // converted fingerprint
-    if ((rv = fp.search(1, &id, &score)) != ZFM20::ERR_OK) {
+    if ((rv = fp.search(1, id, score)) != ZFM20::ERR_OK) {
         if (rv == ZFM20::ERR_FP_NOTFOUND) {
             cout << "Finger Print not found" << endl;
             return 0;