Fix the capture_manager.py behaviour of adding multiple captures with the same file name and path

[JoshHarris2108]

The capture manager should be able to handle being told to add captures with the same file and path by iterating a number on the end of the file such as :

file path = "/data/babyd/
file name = "test_100k_frames"

add first capture, with full path+name of :

/data/babyd/test_100k_frames

add a second and third capture, with full path+name of:

/data/babyd/test_100k_frames_1
/data/babyd/test_100k_frames_2

other subsequent captures added with the same file_path+name should be iterated as above. This currently works if a capture is duplicated through the capture manager's duplication funciton, but not when added manually.