Moved "use Algorithm::Diff" from IOS to Cisco.pm
Simplified method write_mem.
Added Cisco generic write_mem method.
Moved noop methods for schedule / cancel reload
get_ip_prefix no longer accepts ip/mask
Fixed simplified method write_mem
Unified method check_max_acl_entries for cisco dev
Simplified error printing in checkinterfaces
Removed unused method check_firewall.
Fixed error message
write_mem checks for COMPARE mode now.
Simplified methods transfer and write_mem
Fixed: CMD2STDOUT -> COMPARE
Added prefix "> " to output of cmd_ok
Call cmd_check_error even if @$lines is empty.

This is needed in Linux.pm, because it should call status_ok
even if output is empty.
Multiple params for abort_cmd, like abort
New classes Cisco_Router and NX_OS

Moved common methods of NX_OS and IOS to Cisco_Router.
Moved schedule_reload and cancel_reload to Device.pm
Made different methods cmd_check_error more similar.
New method resequence_cmd for IOS and NX_OS
Bug fix: use new name in sub define_acl
Added support for object-groups.
Parser allows leading _skip now.