[qpfile] Support K frametype

[shinchiro]

x264 has 6 choices when defining frametype Frametypes: I,i,K,P,B,b

But x265 doesnt has K type. May I request to add K type as well?

[Steve Borho]

Is K simply an alias to I (IDR)?

[shinchiro]

From x264's help:

--qpfile <string>     Force frametypes and QPs for some or all frames
                      Format of each line: framenumber frametype QP
                      QP is optional (none lets x264 choose). Frametypes: I,i,K,P,B,b.
                          K=<I or i> depending on open-gop setting
                      QPs are restricted by qpmin/qpmax.

I just think its best to keep x265's cli similar with x264's cli if possible

[Deepthi Nandakumar]

Adding Frametype 'K' (fixes #161)

→ <<cset 5932bdaf8eae>>

[Deepthi Nandakumar]

x265cli: clarifying frametype 'K' (refs #161)

→ <<cset e951ab673b1c>>