[Merge] point_of_sale : Improvements in POS module

addons/point_of_sale/__init__.py

addons/point_of_sale/__openerp__.py

addons/point_of_sale/account_bank_statement.py

addons/point_of_sale/pos.py

addons/point_of_sale/pos_account_bank_statement.py

addons/point_of_sale/pos_view.xml

addons/point_of_sale/report/__init__.py

addons/point_of_sale/report/report_cash_register.py

addons/point_of_sale/report/report_cash_register_view.xml

addons/point_of_sale/report/report_pos_order.py

addons/point_of_sale/report/report_pos_order_view.xml

addons/point_of_sale/security/ir.model.access.csv

addons/point_of_sale/singer_statement_demo.xml

addons/point_of_sale/statement_view.xml

addons/point_of_sale/wizard/pos_box_entries.py

addons/point_of_sale/wizard/pos_box_entries.xml

addons/point_of_sale/wizard/pos_box_out.py

addons/point_of_sale/wizard/pos_box_out.xml

addons/point_of_sale/wizard/pos_close_statement.py

addons/point_of_sale/wizard/pos_open_statement.py