UI: Cleanup and fix labels and descriptions in various places

Changes include using proper and consistent grammar, simplifying
phrasing, using correct terminology, and not including python API
identifiers in tooltips.

Differential Revision: https://developer.blender.org/D9924

release/scripts/startup/bl_operators/uvcalc_lightmap.py

@@ -614,8 +614,8 @@ class LightMapPack(Operator):
     PREF_PACK_IN_ONE: BoolProperty(
         name="Share Texture Space",
         description=(
-            "Objects Share texture space, map all objects "
-            "into 1 uvmap"
+            "Objects share texture space, map all objects "
+            "into a single UV map"
         ),
         default=True,
     )