extensible advanced menu

import/export commands not restored yet
rename rcloud.NotebookInfo -> rcloud.notebook.info, 1/2

the files
rename rcloud.NotebookInfo -> rcloud.notebook.info, 2/2

the contents
remove ancient defunct editor.search code
import/export finally leave the shell_tab

this completes advanced menu extensibility
and moves half the code out of shell_tab!
remove unnecessary id field from settings

(because i am remarkably stubborn)
restore not showing date for terse dates

i broke this in 61cb107907ab4d25b6abc8c8821399d1f21ba8da
because i forgot format_date_time_stamp is used for both notebooks & versions
only disappear dates if there are appearing commands

also some minor cleanup of notebook commands (ostensibly for efficiency)
build.sh build rcloud.packages/* by default; also --break option

for @s-u
we now have
 --base: just js, rcloud.support, rcloud.client
 --core: .. plus rcloud.packages/* (the default)
 --all: .. plus packages/*

in addition, because this annoyed me
 --break: die when any package fails to build
Merge branch 'develop' into feature/everyway-extensible