lvconvert: enhance automatic settings of possible (raid) LV types

lvconvert: enhance automatic settings of possible (raid) LV types

Offer possible interim LV types and display their aliases
(e.g. raid5 and raid5_ls) for all conversions between
striped and any raid LVs in case user requests a type
not suitable to direct conversion.

E.g. running "lvconvert --type raid5 LV" on a striped
LV will replace raid5 aka raid5_ls (rotating parity)
with raid5_n (dedicated parity on last image).
User is asked to repeat the lvconvert command to get to the
requested LV type (raid5 aka raid5_ls in this example)
when such replacement occurs.

Resolves: rhbz1439403