Add addition date formats

[khoivan88]

What:

1. This commit adds a few extra date format (mm/dd/yyyy as well as
   yyyy-mm-dd for no confusion regardless of wherever in the world you are
   using OE).
2. This commits also add function so that the open_date and
   order_date when import can be recognize in any format (dd.mm.yyyy or
   mm/dd/yyyy or mm-dd-yyyy).
3. This also help with date search. Now user can type date in search box
   in any format (dd.mm.yy or mm/dd/yy)

Why: with OE is being used more and more all over the world, this
function will help users not from Germanny to find it even more useful