Homogenization of format of functions which do have an own page already
Better description of WinExist()
Removed WinExist() documentation and replaced by link to own page (IfWinExist.htm)
United documentaion of StringLen and StrLen() on page StringLen.htm

Adapted Links to StrLen() linking to page StringLen.htm
Corrected messed up html
Corrected links to StrLen() and WinExist()
Consistent pagetitle on StringLen.htm
More HTML Cleanup

Removed obsolete class="CommandSyntax" (see https://trello.com/card/remove-css-class-commandsyntax/4ff142712c442e040466599d/37)
Removed empty \<a\> and \<em\>-Tag
Merge pull request #41 from hoppfrosch/8-Own_pages_for_built-In_functions