Factor constants out of ST_SPL
Add outline for ST_Accessibility

(Some methods undefined)
Update outline
Implement All-to-Several and DO test
Add All-to-Several WDO test
 Add All-to-Several RO test
Simplify tests a little
 Add All-to-Several WRO test
Add All-to-Several U test
Add All-to-Several WU test
Add All-to-Many and DO test
Put all-to-several and all-to-many together
Combine DO tests
Finish WDO tests
Finish RO tests
Finish WRO test
Finish U test
Finish WU test
Add ST_Accessibility remarks
Fix reference to ST_Graph