Enhancement - StringTable integration

- StringTable now integrated into Context.
- Docs updated for new "locale" configuration variable.
- StringTable unit tests implemented.

html/config.html

@@ -52,6 +52,23 @@
                   /Users/paul/.task
                 </dd>
 
+                <dt>locale</dt>
+                <dd>
+                  <p>
+                    A locale can be specified as a combination of an ISO 639-1
+                    language code (such as 'en'), and an ISO 3166 country code
+                    (such as 'US'), combined in to specify which strings file
+                    to load ('en-US').
+                  </p>
+
+                  <p>
+                    If a corresponding strings file is found, it will be loaded,
+                    and all subsequent error messages and feedback will be
+                    localized.  It is an error to specify a locale without a
+                    corresponding strings file.
+                  </p>
+                </dd>
+
                 <dt>confirmation</dt>
                 <dd>
                   May be "yes" or "no", and determines whether task will ask for