Update passwordless.md

Following these instructions using Unbuntu 13.10 as client I had error "Agent admitted failure to sign using the key." Adding my RSA or DSA identities to the authentication agent, ssh-agent 
the execute the following command seems to have fixed this:  
```
ssh-add
```
Added pin configuration documentation
Compute module camera instructions update
Updated default pin configuration
Shorten forum URL
Fixed consistency of WiFi spelling in documentation
Fix relative link so it'll work on raspberrypi.org
Merge pull request #110 from tomcrick/master

Fix consistency of WiFi spelling
Merge pull request #105 from XECDesign/dualcam

Add dualcam and pin configuration documentation
Clearing partition table allows writing to a used SD card.

A "dd" on MacOS can fail due to lack of write permissions on the disk device, even when using sudo. This is a measure to protect SD cards from accidental overwritting. Clear the partition table on the SD card. This also sets the disk device permissions to allow writes.
Added pages to describe different models and revisions
Merge pull request #115 from JamesH65/master

Added pages to describe different models and revisions
Correct small typos, and add some links
Attempt to fix one of the Travis build errors
Add change directory into linux dir to Local Building instructions.
Merge pull request #118 from bhamail/master

Add change directory into linux dir to Local Building instructions.
Add note about low gpu_mem values

Fixes #117
HDMI pin numbering fixed

HDMI data lines are D0-D2 and not D0-D3.
Change to using Minecraft Pi from apt
Add Minecraft desktop logo
Remove old terminal image