Continued with customers and rewrite a bit:

Continued with customers and rewrite a bit:
- page show_customer "basicly finished"
- removed double redundant i18n strings (no need)
- added customer's i18n strings (admin)
- now always handle a contact to "cellhpone templates", this is much easier and users/customers don't have cellphones/land-line or fax numbers, only contacts
- added template for administrative links for customers (similar to users)
- added missing navigation rules

Signed-off-by: Roland Häder <roland@mxchange.org>