WIP: Add Wikipedia Zero detection and GUI features.

* If on Wikipedia Zero participating carrier, toast and update chrome.
* When W0 status off, toast and update chrome.
* Display dialog boxes first time ON and first time OFF. Not again, though.
* Update search bar as appropriate.
* Intercept offsite links, but offer setting to opt out of feature.
** Note, general app-level handling of links worth pass in different PS.
* Show latest W0 status within drawer as context clue.
* This version supports a toggle for "zero devmode" for event handling.
* This version uses uniform English off verbiage, gets carrier banner from API.
* Future: Align on i18n approach.
* Future: Remove "zero devmode" option and ensure all listeners working.
* Refer to I7fc92136313a3116b43543c5198d7f7875664293 for the out-of-sync version.

Conflicts manually resolved:
	wikipedia/res/values/preference_keys.xml
	wikipedia/res/values/strings.xml
	wikipedia/src/main/java/org/wikipedia/NavDrawerFragment.java
	wikipedia/src/main/java/org/wikipedia/Utils.java
	wikipedia/src/main/java/org/wikipedia/WikipediaApp.java
	wikipedia/src/main/java/org/wikipedia/editing/DoEditTask.java
	wikipedia/src/main/java/org/wikipedia/editing/FetchSectionWikitextTask.java
	wikipedia/src/main/java/org/wikipedia/interlanguage/LangLinksFetchTask.java
	wikipedia/src/main/java/org/wikipedia/networking/ConnectionChangeReceiver.java
	wikipedia/src/main/java/org/wikipedia/page/LinkHandler.java
	wikipedia/src/main/java/org/wikipedia/page/PageActivity.java
	wikipedia/src/main/java/org/wikipedia/page/SectionsFetchTask.java
	wikipedia/src/main/java/org/wikipedia/search/SearchArticlesFragment.java
	wikipedia/src/main/java/org/wikipedia/search/SearchArticlesTask.java
	wikipedia/src/main/java/org/wikipedia/settings/SettingsActivity.java

Change-Id: I05f5d847cfbb996915394750e01999addf2abba9