Start dark theme - action bar and expandable list view backgrounds
Fix dark ActionBar style
Background colours for folder and feed rows
Initial work on preference to switch themes
Apply theme preference to all activities that don't extend NbActivity
Folder/feed text and highlights on the main view
Background and font colours for all stories/shared stories and saved stories selectors
More dark backgrounds
Move lookup of feed adapter colours to a helper class
Story adapter colours for dark theme
Support dark theme on reading webview
Change link and pre/code colours for webview with dark theme
actionbarBackground was missing from dark theme. Fixes intelligence selector background.
Background for reading item header
Fix text colour for story title in reading header.
Date and author text for reading metadata.
Apply dark theme to tags
Dark theme for save/share story buttons
Switch theme automatically following preference change
Fix story context preview for dark theme