alphabetical quesiton number bug   #65

regular expression to parse page and question number now tolerates
alphabetical characters between 'pg' and the page number, as well as
between 'q' and the question number.

In case of error, e.g. 'pg5_q_3.html' or 'pg5_q.html', it will
give an error to the admin, and set the page and question numbers to -1.
This can be corrected manually, if there are many errors, the admin may
choose to delete and upload again.