Fixing setting speed limit of torrent in WEBUI

Fixing setting speed limit of torrent in WEBUI when global speed limit
is not set.
Split filterparserthread into .h and .cpp
Move libtorrent includes to .cpp

This commit probably fixes #2119.

The only important change in this commit is moving
session::get_ip_filter() from FilterParserThread::processFilterFile() to
FilterParserThread::run(). Previously we called it in main thread, but
now we calls it in worker thread. I don't now what libtorrent contract
about threads, but I assume that if it is ok to set_ip_filter from
other thread, it is ok to get it.
Split statusbar into .h and .cpp
Split trackerlogin into .h and .cpp
Fix a warning
WebUI: Fix WebAPI returned data.
WebUI: Add charset attribute to text content types.
WebUI: Fix upload window closing on old browsers.
Remove extra double quotes
Add alt attribute to images
Add type attribute to style tag
Focus username input on load
Remove "Downloaded" from transferlist header and reduce column width
Change background color of filterlist on hover
Change background color of rows of torrent content
Don't show white parts when hovering over the elements of the menu
Alternate background color for torrent content

CSS3 support required.
Center vertically "+" image in tracker list
Change color of table header in bottom panel and add some padding