More router manuals added

Added links to the following router and gateway manuals:

- AT&T: 4 replacement/self-install guides

- Linksys: 1 user manual

- Technicolor: 5 user manuals, 1 open source report

- Verizon: 1 installation guide

- Westell: 1 remote management device reference guide

Cox router and gateway manuals

Self-installation guides:
- Vertiv WiFi Modem / Non-WiFi Modem (2017)

Easy Connect guides:
- Panoramic Wifi Gateway (model not specified)
- Technicolor CGM4331 / CommScope TG4882 Panoramic Wifi Gateway
- Technicolor CGM4331 Panoramic Wifi Gateway for Fiber
- Technicolor CGM4981 Panoramic Wifi Gateway
- Technicolor CGM4981 Panoramic Wifi Gateway for Fiber

Technicolor router manuals

Setup and user guides:
- Technicolor DOCSIS CGM4331XXX Gateway (2019)

- Technicolor MediaAccess TC8305C Gateway (2013)
- Technicolor MediaAccess TC8717C Gateway (2014)

- Technicolor MediaAccess TC8717T Gateway (2014)

Operations guides:

- Technicolor CGM4231 Wireless Gateway (2018)

Easy Connect guides:

- Technicolor CGM4331 Panoramic Wifi Gateway
- Technicolor CGM4331 Panoramic Wifi Gateway for Fiber
- Technicolor CGM4981 Panoramic Wifi Gateway

- Technicolor CGM4981 Panoramic Wifi Gateway for Fiber

Open Source Reports:

- Technicolor CVA4001CHR (2018)