1. Based on the feature PCD value, browser will decide whether to gray out the read only menu.
2. Update Browser to provide the customization possibilities.
3. Refine the code logic for browser and display engine.
git-svn-id: https://svn.code.sf.net/p/edk2/code/branches/UDK2010.SR1@14638 6f19259b-4bc3-4df7-8a09-765794883524
