* Add CommandIterator.ConVarFlags property
Allow to access the convar flags `FCVAR_*` value from the iterator.
The CommandIterator.Flags property should have been called `AdminFlags`,
but it's too late to change that now.
* Switch admin help menu to use CommandIterator.ConVarFlags
No need to lookup the convar again.
* Deprecate CommandIterator.Flags
Rename it to .AdminFlags now that we have two kinds of flags exposed
on the iterator.