Bug 29762: Change field names from "Mobile" to "Other phone"

Bug 29762: Change field names from "Mobile" to "Other phone"

This Patch changes the field name for "Mobile" to "Other phone"
in Patron batch modification.

To test:
1. Apply the patch
2. Go to Tools -> Batch Patron Modification and add some patrons
3. Hit "continue"
4. Verify that in the list of patrons you selected, the field
"Mobile" has been replaced by the field "Other phone"
5. Verify that down below in the fields to be batch modified,
the field "Mobile" has also been replaced by the field "Other
phone"
6. Add some data into the field "Other phone" (e.g. 12345 or
some other number) and hit save
7. Confirm that the field was correctly modified and is still
named "Other phone"

Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>