mesh: Add mesh-main.conf file with general mesh configuration

mesh: Add mesh-main.conf file with general mesh configuration

This adds key file with default settings for the mesh daemon.
The following settings are included:

    Beacon:          Default setting for to indicate whether
                     secure network beaconing is enabled for a
                     node whose Beacon state hasn't been configured
                     by a configuration client, i.e., this setting
                     apllies to a newly provisioned, created or
                     imported node.

    Relay:           Default setting for supporting relay

    Friendship:      Default setting for supporting Friendship

    CRPL:            Default depth of replay protection list.

    FriendQueueSize: Default size of friend queue: the number
                     of messages that each Friend node can store
                     for the Low Power node.

    ProvTimeout:     Provisioning timeout in seconds.

Change-Id: Ia5f40ef9d5d866e8d94a2ff5cac7cf6339015eca
Signed-off-by: Anupam Roy <anupam.r@samsung.com>