Add axis labels if not provided, fixed AMM variable name in the example.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@294 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Fixed lmAMM call for multiple firms, fixed lmAMM for single firm: handle univariate series gracefully.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@295 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Added plotting to examples, added eventstudy example using lmAMM.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@296 edb9625f-4e0d-4859-8d74-9fd3b1da38cb
Made print and summary functions same, summary is calling print, can be changed at a later time.

git-svn-id: svn://svn.r-forge.r-project.org/svnroot/eventstudies@297 edb9625f-4e0d-4859-8d74-9fd3b1da38cb