Adding SeLite add-ons to /download/ page.

Fixes Issue #7568

Signed-off-by: Luke Inman-Semerau <luke.semerau@gmail.com>
adding link to Dart webdriver bindings
adding crosswalk driver to list of driver implementations

Fixes Issue #7580
BrowserStack is our first official Selenium sponsor!
header for top sponsors
header for top sponsors
Updated link as per Ritesh @ BrowserStack
Updating IDE release to 2.6.0
sauce labs sponsorship
clarification of logo sizes and use of funds
Adding a link to Tcl binding. Fixes issue 7800
Fixing a typo. Fixes issue 7769
Fixing a typo. Fixes issue 7591