#42 Optimize away string concatenations

Even for a small number of small joins, appending to a list and then doing a string join on the list can be a lot faster than doing repeated string concatenation. Since there are a large number of places in the codebase where we do a whole bunch of repeated string concatenations, one "low hanging fruit" for optimization would be to replace those concatenations. It would also be good to do some tests to see if this actually makes a difference in terms of speed of, say, a page load.