[fppconvert] Simplify fppconvert build

Dan Kulp has made some enhancements to xLight's TabConvert.cpp that
allows us to use it directly without having to munge the source
file anymore, so this commit removes our scripts and changes
fppconvert.cpp to use xLight's TabConvert.cpp directly.  Thanks Dan.
[fppconvert] Cleanup some files missed in 868e43d
Merge branch 'master' of github.com:FalconChristmas/fpp