QuickLinks: add USSD Dialler

 Tablets like N7 3g, N7 LTE, Tablet Z LTE have GSM connections
 but do not support voice calling hence the Dialer is disabled
 on these devices. But the Dialer could be needed to dial USSD
 codes to check balance, recharge balance, pay bills, enter
 phone settings screen (*#*#4636#*#*) or view IMEI number
 (*#06#).

 This enables a link to the Dialer from Settings but to make it
 visible the boolean "needs_ussd_dialer" needs to be set true
 via overlay (packages/apps/Settings/res/values/bools.xml)

 By default the bool is set false and this option is not displayed
 as majority devices do not need this.

Change-Id: Ie6d08f87b9f7d1516afe971704777a49d015be58
Signed-off-by: Arnav Gupta <championswimmer@aokp.co>

Conflicts:
	res/xml/settings_headers.xml