Updated App to support Android 5.0 and more

App now uses SDK version 21 meaning it is now ready for Android 5.0
Lollipop.

The app now utilizes the appCompat library so back porting the Material
design them to API 18 is possible (Can go lower, but app’s minimum API
level is 18).

The app also includes a poker yoke for sample rates by utilizing a seek
bar / slider to limit the range of user inputs.

The app now makes sure the sampling rate, start frequency, step size
and number of increments are synced between activities.

CompatLibrary dependencies have now been moved to an external library.
To compile the app on a system other than mine, you must include the
external library. The library is the appCompat-v7 library provided in
the android SDK.