Issue 261 Fix For The Continue Button

I've changed how the continue button searches for the latest saved game so that it can search all the directories which are in the saved game directory.

Before this change the continue button code expected there to only be an Autosaves directory and would crash the game if there was other directories in the saved games directory.

New functions
-------------
tree_ctrl.lua:FileTreeNode:
+isDirectory()
+getMostRecentlyModifiedChildFile(file_name_filter):
This new function is now the function responsible for finding the latest saved game for the continue button to load. It is called recursively for all of the directories in the saved games directory.
Merge pull request #265 from JASheppard/continue_butt_261Fix

Issue 261 Fix For The Continue Button
Games are now always paused when the award screen appears

Previously games would only be paused when the game speed was set
to "Speed Up".
Merge pull request #287 from JASheppard/issue286Fix

Games are now always paused when the award screen appears
Fixed Issue #288: The Award Screen "Speed Up" Key Bug

This commit fixes an issue which made the "Speed Up" key pause
the game instead of speed it up after the award screen was closed.
Merge pull request #289 from JASheppard/288_Fix

Fixed Issue #288: The Award Screen "Speed Up" Key Bug