Build 49

- added: postdata accepts 'subpage' as value to expand. This enables subpages defined by postdata.
- added: subpage list accepts 'index_variable_element' as value to expand
- added: new feature sort, enables to sort multi value elements for a part of its value
- bug fixed: credits and channel elements in xmltv follow the xmltv standard
- bug fixed: forward looking dst switch didn't work properly for the 'spring' switch.
- added: new option in operations with indices, operators: start (optional)length/(optional)repeat
          works for commands substring, remove and replace.
- url subpage list builder with variable, e.g.
          subpage.format {list(step=21600 count=3)|'index_variable_element'}
- bug fixed in calculate: syntax like : element.modify {calculate(format=date,unix)}