Back ends and work sequences

Project that use work sequences will need two additional processes:

Component BOINC-supplied part project-supplied part
Work sequence relocater: detects work sequences whose hosts have failed, and relocates them to other hosts. A program seq_relocate Some parameters used by seq_relocate
Work sequence validation and accounting: Similar to result validation, but for work sequences. A program seq_validate An application-specific function, linked with seq_validate, that compares sets of redundant results.