[FS#1130] Add partial import for settings

[LEDE Bugs]

A new Flyspray task has been opened.  Details are below. 

User who did this - tr1cks (tr1cks) 

Attached to Project - LEDE Project
Summary - Add partial import for settings
Task Type - Bug Report
Category - Base system
Status - Unconfirmed
Assigned To - 
Operating System - All
Severity - Low
Priority - Very Low
Reported Version - Trunk
Due in Version - Undecided
Due Date - Undecided
Details - Sometimes it's very necessary feature. For example after upgrade from OpenWRT to LEDE my router works fine with default settings. But after import my configuration, DNS and DHCP IPv4 not working at all. And it's hard to determinite what settings responsible for this, because you can only import all or nothing. I suggest add dialog with checkboxes to import configuration process.

More information can be found at the following URL:
https://bugs.lede-project.org/index.php?do=details&task_id=1130