make docs match usage and roxygenize, bumped to 0.8.19

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/blotter@1607 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
- patch firstCross to coerce to numeric, if necessary


git-svn-id: svn://svn.r-forge.r-project.org/svnroot/blotter@1608 edb9625f-4e0d-4859-8d74-9fd3b1da38cb