User preference to hide Python references in Tooltips.

Add a "Save user settings" operator entry in the File menu, avoids having to open User Preferences to save layout changes.

Fix for [#24292] When rendering with the stamp feature the scene opt. affects the seq. strip placement
Fixed typo.

Commented out some unimplemented operators, avoids gray text in the UI
Also I noticed there's a check on strip.type == 'EFFECT', which can never be true because strip.type actually contains the type of effect, e.g. "GLOW", "ADD" etc. Not a big problem currently because it's not used.

Added visible_bases and visible_objects to screen Context.
Also fixes [#21576] bpy.ops.object.select_all() doesn't function

Bugfix for [#21582] Adjusting material color (color picker) crashes

This fixes only the crash, which was due to buffer overrun for col Hex char buffer. It doesn't actually fix the real issue of overflowing the color values up to infinity.

Added splash screen item in the Help menu. Not sure why it wasn't there in the first place? It's used to get the revision number and if the intention was to add a more adequate "About" window it can be replaced later.

Fix for [#21773] Cast Modifier cant use empties as centers

Based on the assumption that requiring object targets to be OB_EMPTY makes any other object compatible as a target. If the assumption is wrong can be reverted. Only the Cast modifier uses this at the moment and to me it looks like Cast only uses object transform so should be fine.

Remove object type check in Cast Modifier deformation, was wrong now that Curves support modifiers.
Also fixes [#21742] Crashes when adding a Cast mod after a Screw mod on a Curve Object

Fix for #21420, Minor bug with editing keymaps

Disable add item button for non-editable keymaps