support meta commands (eg to manipulate history etc)

[timotheecour]

https://github.com/wheineman/nrpl allows using meta commands, eg:

> :help
:? - print this help
:help - print this help
:history - display history
:clearHist - clear history
:delete n[,m] - delete line or range of lines from history
:load filename - clears history and loads a file into history
:append filename - appends a file into history
:save filename - saves history to file
:run - run what's currently in history
:version - display the current version
:quit - exit REPL
:remove varname - remove variable

this would be quite useful, eg also for enabling #5 via, say, :brace=on or :brace=off

can these be implemented as regular procs?

(and inim would automatically call from inim_special_commands as z import nil)
eg:

z.help()
z.history()
#etc

[Tangdongle]

If it's possible to get a list of symbols and functions from nimsuggest, I reckon we can implement ipython's behaviour, ie if you define a built in command within ipython, it overrides that builtin command.