Fix review comments for pull request.

1) Don't expose gui mode to the causual user. Hide under the DEVELOPMENT_MODE
   #define.

2) Add accessors for the ModifierLinkableList's interesting fields.

3) Free the ModifierLinkableList from modifier_linkable_list(). This allows
   us to make the free function static.

4) Rename modifier_linkable_list() to update_modifier_linkable_list().

5) In effects.h, reflect the renaming of update_modifier_linkable_list() and
   correct it's signature.

6) Whitespace fixups in gdigi.c.

7) In the handler for RECEIVE_GLOBAL_PARAMETERS, apply the parameter to the gui.

8) Fixup some merge damage ;-(

9) UnCamelCaseIze some variables.

10) When we create the gui, issue a single call to REQUEST_GLOBAL_PARAMETERS to
    retrieve the globals from the device, instead of polling each parameter
    individually.

effects.h

@@ -118,9 +118,10 @@ typedef struct {
 } Device;
 
 gchar *get_position(guint position);
-ModifierGroup *modifier_linkable_list();
+void update_modifier_linkable_list(GString* msg);
 extern ModifierGroup *ModifierLinkableList;
-void modifier_group_free(ModifierGroup *modifier_group);
+EffectGroup *get_modifier_group(void);
+guint get_modifier_amt(void);
 void get_values_info(EffectValues *values,
                      gdouble *min, gdouble *max, gboolean *custom);
 gboolean get_device_info(unsigned char device_id, unsigned char family_id,