preliminary work for websocket support
add missing files
removed unused functions
Revert "removed unused functions"

Will support websocket client, after all.

This reverts commit 2ad1bb7b4c454ea2070fee72f246ccb60328ca91.
fix stream reading by length
working websocket sample page
refactored, ws closing still broken.
fix line reading on empty streams
ws refactored, kept separated from sktd
protect send with pcall
export shell object for programmatic use
working web shell
mixed http/ws scenario broken
protect it() with pcall
fix concurrence problem in server, support ws
do not attach task
cleanup
documentation , cleanup
Merge branch 'websocket'