WebUI: Make column width less variable in transferlist

Each column has a fixed width that allows to read its content.
The column for the name of the torrents has a variable width with an
upper and a lower constraint.

If the width of the page is not sufficient to fit the table, a scrollbar
will appear.
WebUI: Add column separators in transferlist header
WebUI: Make unselecting torrent simpler

It's now possible to unselect a torrent by clicking it or by clicking
the empty area of the transfer list.
WebUI: Load properties tabs once

Load the HTML structure on the JS code only once and keep the unused
tabs hidden.
WebUI: Fix minor error

No timer is set when the functions are directly called.
WebUI: MochaUI: Check for undefined functions
WebUI: Update torrent properties immediately
WebUI: Remove extra parethesis
WebUI: Decrease frequency of updates

Now that the properties are loaded immediately when the selected torrent
or the property tab is changed, the frequency of the updates can be
reduced without affecting the user experience.

General: update every 5 seconds (10 if qBT is not reachable)
Tracker list: update every 10 seconds (20 if qBT is not reachable)
File list: update every 5 seconds (10 if qBT is not reachable)
WebUI: Use divs instead of spans
WebUI: Adjust size of columns in property panels
WebUI: Don't change cursor style for the file list
WebUI: MochaUI: Show entire error message