closes#619
- check if uploaded image name exists in month/year path
- if unique then save
- if not unique then add -1 to the end of the name eg. image-1.jpg
- if image-1.jpg exists then increment to -2
- keep going until a unique name is found
- uses tail recursion as normal path will be to save the first filename and deep recursion will be the exception
- (the alternative of loading the names of all the files in the directory could result in a large in memory array)
