Refactor to use groups between network layers to make them less coupled and reusable:
link_frame (ethernet etc)
inet_packet (ipv4,ipv6 etc)
ip_packet (tcp packet (not stream), udp segment etc)
Rename data to payload as i think it makes more sense for network data
Basic support, can also do CER and DER but without any extra validation.
No schema support.
Redo format doc.md usage a bit, now format/<dir>/<format>.md instead.
Related to #20
Remove bitio.Buffer layer. bitio.Buffer was a kitchen sink layer with helpers
now it's just a buffer and most functions have been moved to decode instead.
bitio package now only have primitive types and functions simialar to standard
library io and bytes packages.
Make nearly eveything internally use bitio.Bit* interfaces so that slicing work
correctly this will also make it possible to start experimenting with more
complicated silcing helpers, ex things like:
breplace(.header.bitrate; 123) to get a new buffer with bitrate changed.
Move scalar into own package.
Split scalar code into decode related scalar code (that reads etc) and
scalar code that just transform the scalar value.
Use a scalar.Mapper interface instead of just a function.
Make mappers, assert and validat impement the interface.
