Moved timeshift out of main phys2eventtime function.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@369 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added information about date time class of events when column and a note on usage of findInterval.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@370 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Return NULL if output from any model is NULL.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@371 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fixed test case to use Date class in eventlist.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@372 edb9625f-4e0d-4859-8d74-9fd3b1da38cb