MT#4289 separate customer/ajax and contract/ajax

This is the first step towards separating the
tight coupling of the Customer and Contract Controllers.

Mantis: 4289#c25035
MT#4289 separate customer-/contract- create and ajax_reseller_filter

Mantis: 4289#c25035
MT#4289 fix html-id with invalid symbols

When editing a customer, the helper.name contained a hash symbol (#).
This variable is used to form the id of the html element table, by
stripping spaces from it. Now we also strip the hash, because otherwise
at least jquery will fail to find this id.
MT#4289 move /contract/customer/edit to /customer/edit

So finally, there is no customer-specific stuff left in the Contract controller.
MT#4289 contracts: filter by product and separate terminate

Only show reseller and peering contracts in the
Contracts controller. Also remove the generic create
in favour of the peering/create and reseller/create.

Customer controller now has its own terminate routine to be really
independent from the Contract controller.

Now we can expose the Contract controller in the menu.