Move LoggingEvents.java to android-common & add UserHappiness

The LoggingEvents move will allow Gmail, Voice Search and other apps to
access the LoggingEvents needed. This file will replace
packages/inputmethods/LatinIMEsrc/com/android/inputmethod/voice/LoggingEvents.java
vendor/google/apps/VoiceSearch/apps/VoiceSearch/src/com/google/android/voicesearch/logging/LoggingEvents.java

In addition to moving the file, I have added 3 new fields:
TIMESTAMP, IME_TEXT_ACCEPTED, CALLING_APP_NAME. I needed to
create CALLING_APP_NAME b/c I can't re-use EXTRA_APP_NAME
because that is reserved for one of two values: voice
search or voice IME.

I added another file to android-common: UserHappinessSignals
This can be imported by different applications to broadcast
various user happiness metrics. It is currently used by Gmail's
CompseActivity.java to indicate that a user "accepted" the IME
text when they pressed the send button.

Change-Id: Ia859140facb7fb66a12706735d5132ba9eaa5ea0