[FEATURE] Added v:if, deprecating v:if.condition / v:if.condition.extend

Examples:

```xml
<v:if stack="{0: {0: 'foo'}, 1: '==', 2: {0: 'foo'}}">
	<f:then>IF THEN (YES)</f:then>
	<f:else>IF ELSE</f:else>
</v:if>
```

```xml
<v:if stack="{0: {0: 'foo'}, 1: '==', 2: 3}">
	<f:then>IF THEN</f:then>
	<f:else>IF ELSE (YES)</f:else>
</v:if>
```

```xml
<v:if stack="{0: 1, 1: '==', 2: 1, 3: 'AND', 4: 1}">
	<f:then>IF THEN (YES)</f:then>
	<f:else>IF ELSE</f:else>
</v:if>
```

```xml
<v:if stack="{0: 1, 1: '==', 2: 1, 3: 'AND', 4: {0: 1, 1: '!=', 2: 0}}">
	<f:then>IF THEN (YES)</f:then>
	<f:else>IF ELSE</f:else>
</v:if>
```

```xml
<v:if stack="{0: {0: 'foo', 1: '!=', 2: 'bar'}, 1: 'AND', 2: 1, 3: 'OR', 4: {0: 1, 1: '==', 2: 0}}">
	<f:then>IF THEN (YES)</f:then>
	<f:else>IF ELSE</f:else>
</v:if>
```