Add ability to filter search results based on existing annotation

[vanaukenk]

It would be very helpful to curators to have the option to filter search results based on existing annotation in, e.g. a GAF file.

Possible steps:

• Download annotation files

• Create a table with paper identifiers (e.g. PMID and/or doi) and type of annotation (e.g. C or F or P)

• Filter out papers from searches that match a record in the table (e.g. exclude papers that have already been curated for C)

• Users would have the option to filter all or a subset of papers according to the type of curation

It would also be helpful to be able to flag papers for exclusion from within TPC. In this use case, a record would be added to the table cited above.

[goldturtle]

transferred to TextpressoDevelopers/textpressocentral#17