Initial code for backend CAS and roles management support.
Resolves issue 45.
Resolves issue 43.
Resolves issue 46.
Resolves issue #44.
Updated admin/view/template/common/header.tpl

Added link to github wiki from the help drop-down
Updated admin/view/template/common/header.tpl

Changed text to "gitwiki"
Updated admin/controller/common/header.php

Added "text_gitwiki"
Updated admin/controller/common/header.php

Changed "documentation" to "upstream documentation"
Updated admin/view/template/common/header.tpl

Changed "documentation" to "upstreamdocumentation" under help menu
Updated admin/view/template/common/header.tpl

Removed ReportsSalesReturns
Removed ReportsCustomerCredit
Updated admin/controller/common/header.php

Removed ReportsSalesReturns (text)
Removed ReportsCustomerCredit (text)
Deleted admin/controller/sale/return.php
Deleted admin/controller/sale/return_form.php
Deleted admin/controller/sale/return_history.php
Deleted admin/controller/sale/return_info.php
Deleted admin/controller/sale/return_list.php
Deleted admin/language/english/sale/return.php
Deleted admin/model/sale/return.php
Deleted admin/controller/sale/contact.php

Sales -> Contact = Sales -> Mail