environments, error messages, and stack traces, oh my!

Changed the way processes are launched.
multishell.openTab and kernel.run now accept the current environment as a parameter.
That new process inherits a copy of the passed environment.
Reduces complexity as the calling process is not required to create a suitable env.
Stack traces have been greatly improved and now include the stack for coroutines that error.

sys/apps/inspect.lua

@@ -110,7 +110,7 @@ page = UI.Page {
 					self.grid:draw()
 
 				elseif event.type == 'grid_select' then
-					multishell.openTab({
+					multishell.openTab(_ENV, {
 						path = 'sys/apps/Lua.lua',
 						args = { event.selected.raw },
 						focused = true,