Implement the Dictionary#clear script function

[gunnarbeutner]

This adds a new user-accessible method to the Dictionary class: clear

Like the name suggests this method removes all items from a dictionary.

[gunnarbeutner]

gunnar@abyss ~/icinga2 (feature/dictionary-clear) $ icinga2 console
Icinga 2 (version: v2.8.4-797-g73f69e89d)
Type $help to view available commands.
<1> => d = { a = 3, b = 5, c = 7 }
null
<2> => d
{
	a = 3.000000
	b = 5.000000
	c = 7.000000
}
<3> => d.clear()
null
<4> => d
{
}
<5> =>

[Crunsher]

What's the advantage of this over d = {}?

[gunnarbeutner]

d = {} creates a new dictionary, if there are references to the old dictionary elsewhere (e.g. because a reference to the dictionary was stored in a different variable) those other references will be unaffected by that change.

[dnsmichi]

We already have Array#clear, so I'm fine with it.

[Crunsher]

<2> => d = {a=5, b={f=2, a=1} }
null
<3> => d
{
	a = 5.000000
	b = {
		a = 1.000000
		f = 2.000000
	}
}
<4> => d.b
{
	a = 1.000000
	f = 2.000000
}
<5> => d.b.clear()
null
<6> => d
{
	a = 5.000000
	b = {
	}
}
<7> => d.clear()
null
<8> => d
{
}