Improve Doc Reference section

Improve Doc Reference section

Patch by Martin Davis

Improve trajectory function section
Improve Long Transaction reference section
Add doc Reference Bounding Box functions section
Move doc Reference SFCGAL section
Move doc Reference Misc function Find_SRID
Move doc Ref ST_PointInsideCircle function
Move doc Ref ST_MemSize function
Move doc Ref function ST_Accum to Processing functions
Disable doc Ref Misc Functions section

References #4332
Closes https://github.com/postgis/postgis/pull/383

git-svn-id: http://svn.osgeo.org/postgis/trunk@17346 b70326c6-7e19-0410-871a-916f4a2858ee