BRANCH 4.1:
   improved SelectFilterElementWdg to use a search instance when being run
   improved the use of SelectFilterElementWdg with column starting with "connect"
   added the support of "connect" in @SEARCH
   fixed add_join() implementation in SQLServer so that the prefix is used before ON
BRANCH 4.1:
  improved ExpressionElementWdg handling of datetime object so they are displayed as string
  improved Common.process_unicode_string() to encode only when the src is an unicode object
Merge branch '4.1' of https://github.com/Southpaw-TACTIC/TACTIC into 4.1