Blender Git Loki

* New string property subtype: PASSWORD

When this new subtypes is used, then string of property is hidden using
asterisks, e.g.: mysecretpassword -> ****************

This code was reviewed and modified by Brecht. Thanks very much:
- https://codereview.appspot.com/6713044/

This new subtype of string property is intended mostly for Add-on developers
writing Add-on which communicates with some server (http, sql, ftp, verse,
etc.). When this server requires user authentication and user has to type
username and password, then current API didn't allow to type 'hidden' password,
e.g. when you want to demonstrate this script, then everybody can see this
security password. Some examples of Add-on which could use this new subtype:
- On-line database of textures
- Integration of render farm
- Integration of Verse

Security Notes:
- You can copy paste hiddent string of property from text input using (Ctrl-C, Ctrl-V),
but you can do this in other GUI toolkits too (this behavior it is widely used).
- Text of string property is stored in plain text, but it is widely used in other
GUI toolkits (Qt, Gtk, etc.).

Simple examples:
- https://dl.dropbox.com/u/369894/draw_op_passwd.py
- https://dl.dropbox.com/u/369894/blender-password.png