Display workshop location

[mika018]

Whilst doing this I realsied that we are not storing a City name as part of the location for the workshop. I have therefore included it in workshop table, updated the Database Schema wiki to reflect that and included it in the WokrshopForm so that it is collected when creating workshops.

We can now show both virtual

and physical locations in the WorkshopListing page.

Closes #31

[harryndavies]

This is looking good, nice one!