MAINT-8877: Fix the XML to fix the sizes of the dialogs. (also enforce single instance)

indra/newview/skins/default/xui/en/floater_edit_ext_day_cycle.xml

@@ -3,13 +3,14 @@
         layout="topleft"
         name="env_edit_extdaycycle"
         help_topic="day_presets"
-        save_rect="true"
+        save_rect="false"
         title="Edit Day Cycle"
         width="705"
         height="650"
         min_width="705"
         min_height="650"
-        can_resize="true">
+        single_instance="true" 
+        can_resize="false">
 
     <!-- obsolete?, add as hint for 'save' button? -->
     <string name="title_new">Create a New Day Cycle</string>

indra/newview/skins/default/xui/en/floater_fixedenvironment.xml

@@ -2,20 +2,19 @@
 <floater
         can_minimize="false"
         can_tear_off="false"
-        can_resize="true"
+        can_resize="false"
         can_drag_on_left="false"
         can_close="true"
-        can_dock="true"
+        can_dock="false"
         bevel_style="in"
-        height="500"
+        height="550"
         layout="topleft"
         name="Fixed Environment"
         save_rect="true"
         title="Fixed Environment"
-        save_dock_state="true"
-        save_visibility="true"
+        save_visibility="false"
         single_instance="true" 
-        width="650">
+        width="750">
     <layout_stack name="floater_stack"
             left="5"
             top="5"

indra/newview/skins/default/xui/en/panel_region_environment.xml

@@ -29,8 +29,8 @@
                             valign="top"
                             top_pad="20"
                             text_color="white">
-Parcel environmental settings are 
-disabled on legacy regions.
+No Parcel parcel is selected. Environmental 
+settings are disabled.
             </text>
         </layout_panel>
         <layout_panel