also fix error check and report the message rather then print it.

- remove unused imports
- remove/comment unused vars
- fix for some bugs with unused vars being used

update_tag() tags for depsgraph update only, update() executes normal recalculation and creates edge data.

Removed the "Duplicate and flatten" button from modifiers and added to to the shape_key specials dropdown like the others. 

READ THIS TO AVOID A LOT OF WORK!

New way of linking to tracker pages: just use the parameter "aid" (artifact ID),
to avoid a lot of manual updates later in wiki and svn.

Example:
=========

OLD WAY TO LINK TO TRACKER
-----------------------------

Complete url of a script in Upload
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=467

If we move this in contrib this url will become
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=468
467 becomes 468, so we have to update this in wiki page.

Later on, when this moves into Trunk, the url will become
http://projects.blender.org/tracker/index.php?func=detail&aid=25349&group_id=153&atid=469
468 becomes 469, so we have to update the url in wiki page and svn.

Annoying!

NEW WAY TO LINK TO TRACKER
-----------------------------

Best way to link to tracker page is using:
http://projects.blender.org/tracker/index.php?func=detail&aid=25349

Use "func=detail"
Use "aid"            (which is the "artifact ID")

DON'T use "group_id" (which is the project ID, bf-extensions is project 153)
DON'T use "atid"     (which is the "artifacts tracker ID")

Like this, the url is unique, and we will avoid to update wiki pages and svn after moving pages
 


[[Split portion of a mixed commit.]]

[[Split portion of a mixed commit.]]