Convert a wikilink to markdown link

procedure to convert a wikilink to markdown link
bijvb. [[4.boekhouding]] ==> [boekhouding](4.%20boekhouding)

procedure

1/ remove dubbele [ & ]
[[4.boekhouding]] ==> [4.boekhouding]
2/ copy to string2
3/ string 2 : replace [ & ] with ( & )
4/ string 2 : replace all {space} with %20
5/ concat string & string2

optional remove leading numbers with point (only in string 1)