Formats a string for use in a URL.
This function converts blank spaces and reserved characters to an escape sequence.
The only parameter is the string.
Returns a string formatted for use in a URL.
Formats the string home page as home%20page:
<$url("home page")$>
Formats the string home/page as home%2fpage:
<$url("home/page")$>
Formats the string home?page as home%3fpage:
<$url("home?page")$>