Fixes initialisation of filenames in main

- Main function’s declaration of filenames now initialises the pointer
to zero.
Adds progress information to main function

- Main function now includes printf statements to describe current
progress.
Changes LoadTree read method

- Method for loading the saved tree state to memory has been altered,
removing the need for two loops. This change brings tree loading in
line with ahills60/DBSimulator@d26961e1d7d89abdccd93839597cd478139b28d5.