Feature adding filters to homescreen

As I follow many series, my table on the home screen is very long and it takes a lot of time to find a particular series or a series which has a given status.

### New Feature

You have now the following filter options for the columns on the home page
* **Next Ep**: Dropdown with
 * All
 * Within 3|7|14 days 
 * Within a month
* **Show**: Input search field
* **Network**: Dropdown of all available networks taht are inside the table
* **Quality**: Dropdown with
 * >= SD
 * >= HD
 * >= HD720p
 * >= HD1080p
* **Downloads**: Dropdown with
 * Downloaded all
 * Downloads unfinished
 * no episodes found
* **Status**: Dropdown with all stati

This feature has been implemented using the tablesorter filter widget.

### Other changes

Percentage calculation of download progress is now done in Python instead of Javascript. This removes a lot of unneccessary Javascript code.