Started work on formatting multiple-file coverage output

Coverage info is currently stored in a JSON array of JSON
documents with each document storing coverage data of a
single file.
Fixed trailing comma problem in printAndDeleteList

Instead of just checking if list data is an empty list,
program checks if it is an empty list chain, which is a list
(of a list of...) an empty list.
Fixed trailing comma in multiple file printing

Updated prototypes of printAndDeleteList and output_intermediate_file
to return 1 on success and 0 on failure. Failure occurs when
printAndDeleteList attempts to print a list with no coverage information.
If such a list is encountered, it is not printed.
Also removed comma checking in printAndDeleteNode.
Merge pull request #9 from mvankeulen94/update

Fixed trailing comma problems in multiple file printing, added more in-depth checking of empty lists