change words for better understanding

[james.dupin]

- go to webERP/SelectOrderItems.php?identifier=1329949153
- choose a string for which there will be no return amongst the customer branch name.
- Enter string in "part of the customer branch name"
- click search a first time

The return is correct, only one information message is shown

- on the same page, enter an unknown string again
- click search

There are now 2 messages
---> Information
---> Error message which causes a problem
- either you make it disappear
- or you change the text from "Unable to identify the selected customer" to "Unable to identify a branch"-ish.

- Enter now a string which will return something
- click search

The same error message is shown whilst it found one or several results (use angus for example)
And it keeps showing in all subsequent pages unless you go back from the start (main menu/sales/enter order or quote)

String used in 4 php files, you may have to change the code if the meaning is correct in the other pages.