Added a settings screen and a setting for activating Bluetooth. Bug #28.

briar-android/AndroidManifest.xml

briar-android/res/drawable-hdpi/action_about.png

briar-android/res/drawable-mdpi/action_about.png

briar-android/res/drawable-xhdpi/action_about.png

briar-android/res/drawable-xhdpi/action_help.png

briar-android/res/values/strings.xml

...droid/src/org/briarproject/android/DashboardActivity.java

...ndroid/src/org/briarproject/android/SettingsActivity.java