Fix CMake Install

[jnguyen75]

In this PR:

• Removed header references sei.h (no longer in this project) and avc.c (mistakenly listed as a header file)
• Fixed install() scripts for executable targets

After the fixes:

$ make install
[ 34%] Built target caption
[ 40%] Built target srt2vtt
[ 50%] Built target ts2srt
[ 56%] Built target srtdump
[ 65%] Built target party
[ 75%] Built target flv+srt
[ 84%] Built target flv2srt
[ 93%] Built target rollup
[100%] Built target scc2srt
Install the project...
-- Install configuration: "Release"
-- Installing: ${...path removed...}/bin/flv2srt
-- Installing: ${...path removed...}/bin/ts2srt
-- Installing: ${...path removed...}/bin/flv+srt
-- Installing: ${...path removed...}/bin/party
-- Installing: ${...path removed...}/bin/srtdump
-- Installing: ${...path removed...}/bin/srt2vtt
-- Installing: ${...path removed...}/bin/scc2srt
-- Installing: ${...path removed...}/bin/rollup
-- Installing: ${...path removed...}/lib/libcaption.a
-- Installing: ${...path removed...}/include/caption/utf8.h
-- Installing: ${...path removed...}/include/caption/scc.h
-- Installing: ${...path removed...}/include/caption/cea708.h
-- Installing: ${...path removed...}/include/caption/eia608.h
-- Installing: ${...path removed...}/include/caption/caption.h
-- Installing: ${...path removed...}/include/caption/eia608_charmap.h