Allow NULL option for social networks

[ghost]

Where the candidate has made it known that they do not use or intend to use a particular social networking site such as twitter, facebook or linkedin I feel their should be the option of entering NULL.

I feel the current implementation has two problems:

The fist being that it makes the dataset look incomplete, and may cause members to spend time searching for data that does not exist - #120 .

The second issue is that the blank space might encourage false profiles to be created either by supporters or competitors and I feel it would be worthwhile to remove this temptation where evidence is available that the candidate does not have a profile.