#1182 Add 'excerpt' to the list of title sub-types

[Ahasuerus]

Add 'excerpt' to the list of title sub-types. Its handling will be similar to the other sub-types -- short story, novella, novelette -- except that it will be displayed, in brackets, on bibligraphic pages next to the title. We will also want to programmatically change the 4,350 SHORTFICTION titles which currently end with "(excerpt)": remove "(excerpt)" from the title field and set the title sub-type to "excerpt".

Implementation notes:
1. Do not change title records whose title type is NOT SHORTFICTION
2. Do not change SHORTFICTION records whose title sub-type is not empty

[Anonymous]

May need to create a cleanup report for SHORTFICTION titles ending with (excerpt) AND whose title sub-type is not empty

[Anonymous]

A second cleanup report may be needed: non-SHORTFICTION ending with (excerpt)