WebUI: MochaUI: Check for undefined functions
WebUI: MochaUI: Show entire error message
WebUI: Fix minor error

No timer is set when the functions are directly called.
WebUI: Load properties tabs once

Don't reload HTML on tab change. Load the entire structure once and
keep the unused bits hidden.

Keep also the JS code separately, one file per tab.

NOTE: tabs content is not loaded. This will be fixed in the next commit.
WebUI: Update torrent properties immediately

Don't wait for new data to be fetched, request them as soon as
they are required, i.e. when a property tab is loaded or when a
different torrent is selected.
WebUI: Remove extra parethesis
WebUI: Decrease frequency of updates of property panel

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.

New update intervals:
 * General: 5 seconds (10 if qBT is not reachable)
 * Tracker list: 10 seconds (20 if qBT is not reachable)
 * File list: 5 seconds (10 if qBT is not reachable)
WebUI: Adjust size of columns in property panels
WebUI: Don't change cursor style for the file list

Changing the cursor is misleading, no operation can be done.
WebUI: Add readonly attribute to comment textarea

Torrent comments should not be editable.