Construction of TCollection_ExtendedString from plain C string is fixed to consider input string as UTF-8 in several places (identified as described in notes to #31113).
Message_MsgFile is corrected to load resource file as UTF-8 (unless it has BOM indicating use of UTF-16).
Added tests for use of Unicode in some DRAW commands (bugs demo bug14673_*)
Move debug and upgrade user guides to corresponding folders on upper level
Related: remove "debug" pattern from .gitignore to avoid ignoring relevant folder in dox
