bump version to 13.20
Merge table Supported device and Supported programmable keys
Change you test function keys for Cisco 7912 and 7961G phones
remove old Supported device tables
 Add you test function keys for Cisco 7962 phones
Update test funckey Cisco phone 7961
Update test funckey Cisco phone Cisco SCCP Phone
add changelog to index page
update README for new dependencies (sphinx-git)
move documentation changelog to its own page
clean index page

- 100 char lines
- spaces
- remove mention of Open Hardware
Merge branch 'changelog'
restrict changelog to the html version
Update test funckey snom phone 760
Digium phones support other languages than english
update information on Polycom VVX phones
add search and pagination examples to device REST API 1.1
normalize doc style in REST API /1.1/call_logs
normalize doc style in REST API /1.1/devices
normalize doc style in REST API /1.1/extensions