Added Google IMA Ad Rules sample.

BasicIMASampleApp/build.gradle
BasicIMAWidevineSampleApp/build.gradle
BasicWidevineSampleApp/build.gradle

  * Removed since the common IMA and Widevine logic has been pushed up
    into the parent build.gradle.

BasicIMASampleApp/src/main/java/com/brightcove/player/samples/ima/basic/MainActivity.java
BasicIMAWidevineSampleApp/src/main/java/com/brightcove/player/samples/imawidevine/basic/MainActivity.java

  * Removed duplicate event logger.

  * Removed clickThroughUrl logic.

  * Removed unused POSITION constant.

  * Removed onCreateOptionsMenu() and onOptionsItemSelected().

  * Modified setCuePoints() to take a Source arg and use it to
    enable/disable midrolls.

BasicIMASampleApp/src/main/res/menu/main.xml
BasicWidevineSampleApp/src/main/res/menu/main.xml

  * Removed because no longer used.

BasicIMASampleApp/src/main/res/values/strings.xml
BasicWidevineSampleApp/src/main/res/values/strings.xml

  * Removed no longer used strings.

README.md

  * AdRulesIMASampleApp listing.

build.gradle

  * Added downloadIMA method.

  * Modified subprojects to add IMA and/or Widevine dependencies as
    appropriate.

gradle.properties

  * Bumped up the anpVersion to 4.0.12+.

settings.gradle

  * Added $runAdRulesIMASampleApp check.