Ensure full translatable support.

[wilr]

From http://open.silverstripe.org/ticket/6524.

The outputs of the cmsworkflow module are only very sparsely translated. This is because most messages i.e. in the templates are hard-coded and do not make use of _t(...). Therefore, the module is more or less inusable within non-English environments. For example, when using de_DE it is very chaotic. Moreover, not only the templates like SiteTreeCMSWorkflow_workflowtab.ss are affected, but also:

error/status messages (-> user_error() )
workflow reports including their titles
the relevant entries in the "Access" tab
the titles of the workflow tabs as well es other outputs from updateCMSFields() of i.e. SiteTreeCMSWorkflow.php
the "Created" column of the "Workflow Archive" tab
I regard these missing translations as critical, especially within the templates, since they do not really allow the use of another UI language.