move blog management under main settings activity

- options to add, remove, and manage individual blogs are now all
  managed via the main application preferences activity (same as iOS)
- menu drawer item now opens main preferences activity (should we call
  it "settings" or "preferences"?)
- Settings activity should probably be moved to be a formal
  PreferenceActivity at some point

git-svn-id: https://android.svn.wordpress.org/trunk@933 a6565c4b-a94d-4d28-bb26-aa9e5ab542c0