Add new roclets: depends_roclet in roclet-depends.R and index_roclet in roclet-index.R
Also alter roc_output.namespace function in roclet-namespace.R so that Import field is updated in DESCRIPTION.
Update DESCRIPTION and NAMESPACE files, and added INDEX file to reflect changes of previous commit.
Add documentation for depends_roclet and index_roclet
Comply with R's error reporting conventions.

R usually reports errors with a full path on a separate line. Something like

    Error in source(file = "c:/spinus/works/pbm/protoClasses.R") :
    c:/spinus/works/pbm/protoClasses.R:374:31: unexpected ', '
    373:                                  .initCells(dots,  .self)

It is good to comply with this convention, as some IDEs (for example ESS) can
track this errors and navigate directly to the error location.
fixed \dontrun escape problem
Merge remote-tracking branch 'vitoshka/master' into develop
Merge remote-tracking branch 'vapniks/master' into develop
Merge remote-tracking branch 'jeroenooms/patch_dontrun' into develop