Restructure code.

   This is quite a bit in one commit but it:

       * Splits the app into an app and module so the analysis components
         can be re-used. Also tidied up all the header files in the app.
       * Updates the app_handler to syphon off i2s samples (renamed to i2s_tap)
       * Changes the communication between the i2s tap and the analyzer
         slightly
       * Updates to be able to test based on i2s loopback

   Currently the code only works in simulation (axe command line added to
   Makefile)
Merge branch 'master' into d
Update spectral analysis
Update app to run on XR-USB-2.0-MC board.
Add multiple channel support.
Add more advanced sinewave generation.
Update freqency detection resolution
Tidy up a bit
Make glitch detection relative to amplitude
Add multiple configs
Tidy code up a bit
Fix xscope/simulator config
Add lost signal detection to analyzer
Add more debug output
Move signal generation into module
Rename app
Add eclipse metainfo
Update test target in Makefile
Remove unused ports.
Whitespace changes.
Ensure that the build is the default target (not test).
Creating xpd.xml.