Enhancement: Context settings classbased processor + lexicon/translation fix

I stumbled over the issue, that when I create a context setting, for example with "site_name" (key), "setting_site_name" (name), "setting_site_name_desc" (description) the name and description were not translated via existing lexicon strings (as the setting is the same as in the main system settings...this seems to be due to the modcontextsetting.class.php (in mysql/ and sqlsrv/ folders) setting name_trans and description_trans which then causes the getlist processor for context settings to not look for existing lexicon entries...when name_trans and description_trans are changed to "name" and "description" instead, it seems to work fine.

In the process I quickly replaced the non-classbased getlist processor for context settings with a copy of the class based system settings processor with minor adjustments (not sure if I forgot something, but works fine on my end)