edconf-set-indentation sets the indent and use local variable instead of global.

Squashed commit of the following:

commit ec1b84ac68ab9309a8ece62ec9fb0f6155b8207c
Author: Desmond O. Chang <dochang@gmail.com>
Date:   Tue Mar 4 23:14:23 2014 +0800

    Allow derived mode to use parent mode setting.

    Allow derived mode to use the setting of the closest parent mode which
    exists in `edconf-indentation-alist`.

    E.g., `doctex-mode` doesn't have to add its own setting into the alist.
    Instead, it can use the setting of `latex-mode` if they use the same
    indent variables.

commit 8d0339d0cd2fe287074548a740cda3318c67d2e8
Author: Desmond O. Chang <dochang@gmail.com>
Date:   Tue Mar 4 19:27:34 2014 +0800

    More indentation settings.

commit 46d0fc6cfa6b388714626258addbf9e547516cae
Author: Desmond O. Chang <dochang@gmail.com>
Date:   Fri Dec 13 05:23:31 2013 +0800

    Set indentation by mode.

commit 5cf94a13185aadda80077feecfac4019fb5f25e2
Author: Desmond O. Chang <dochang@gmail.com>
Date:   Fri Dec 13 03:40:56 2013 +0800

    Make all related variables buffer local.

commit df3423d111819b01f3ba20ddac47e389c48d0856
Author: Desmond O. Chang <dochang@gmail.com>
Date:   Fri Dec 13 03:52:48 2013 +0800

    Fix position of docstring.