Added sound to the number buttons

Added sound to the number buttons, can be a different sound for each
button.
Added a very unforgiven validation of the phone number.
reformatted the code a bit, especially the variable names.
Merge branch 'feature_number_sounds' into develop

Conflicts:
	app/build.gradle

app/src/main/java/pidal/alfonso/phonedialergroup1/CheckNumberActivity.ja
va
	app/src/main/java/pidal/alfonso/phonedialergroup1/DialerActivity.java

app/src/main/java/pidal/alfonso/phonedialergroup1/phonefunctions/PhoneFu
nctions.java
	app/src/main/res/layout/activity_check_number.xml
	app/src/main/res/layout/activity_dialer.xml
Deleted landscape dialer view (moved)