Removed Title Bar, Modified List Text Colour

- Added a section of XML to the App's Base Theme which should remove the
title bar only every Activity, or if not at least the Main Activity.
- Fixed some issues with the List Colour, which involved changing the
colour the text colour pointed to from @color/sidebar_txt to
@color/android:textColor="@color/list_select_txt.
- Added a "@color/list_select_hover_txt" option which sets the text
colour when a list item is pressed. For the time being it is the same
colour as @color/list_select_txt, white.