Add the possibility to initialize the classes allocated with the PagedAllocator
Add the possibility to initialize the classes allocated with the PagedAllocator

It uses the (`const T &&... p_args`) forward reference, to avoid copying the
memory in case it's an rvalue, or pass a reference in case it's an lvalue.

This is an example:
```c++
PagedAllocator<btShapeBox> box_allocator;
btShapeBox* box = box_allocator.alloc( btVector3(1.0, 1.0, 1.0) );
```

akien-mga/godot,honix/godot,firefly2442/godot,Shockblast/godot,Zylann/godot,ZuBsPaCe/godot,godotengine/godot,godotengine/godot,akien-mga/godot,Faless/godot,godotengine/godot,Zylann/godot,DmitriySalnikov/godot,vnen/godot,godotengine/godot,Valentactive/godot,vnen/godot,vnen/godot,sanikoyes/godot,guilhermefelipecgs/godot,honix/godot,firefly2442/godot,firefly2442/godot,godotengine/godot,josempans/godot,josempans/godot,Shockblast/godot,Shockblast/godot,vnen/godot,Valentactive/godot,DmitriySalnikov/godot,vkbsb/godot,godotengine/godot,pkowal1982/godot,guilhermefelipecgs/godot,pkowal1982/godot,akien-mga/godot,akien-mga/godot,BastiaanOlij/godot,akien-mga/godot,Zylann/godot,Shockblast/godot,DmitriySalnikov/godot,Valentactive/godot,sanikoyes/godot,BastiaanOlij/godot,vnen/godot,Valentactive/godot,vkbsb/godot,ZuBsPaCe/godot,josempans/godot,Faless/godot,vnen/godot,BastiaanOlij/godot,sanikoyes/godot,BastiaanOlij/godot,ZuBsPaCe/godot,BastiaanOlij/godot,Valentactive/godot,ZuBsPaCe/godot,josempans/godot,vkbsb/godot,BastiaanOlij/godot,sanikoyes/godot,Faless/godot,vkbsb/godot,BastiaanOlij/godot,pkowal1982/godot,vkbsb/godot,Zylann/godot,honix/godot,vnen/godot,guilhermefelipecgs/godot,josempans/godot,Faless/godot,honix/godot,sanikoyes/godot,guilhermefelipecgs/godot,Zylann/godot,firefly2442/godot,godotengine/godot,akien-mga/godot,Valentactive/godot,Zylann/godot,josempans/godot,firefly2442/godot,Valentactive/godot,vnen/godot,Shockblast/godot,Shockblast/godot,vkbsb/godot,josempans/godot,Faless/godot,DmitriySalnikov/godot,sanikoyes/godot,pkowal1982/godot,akien-mga/godot,Faless/godot,pkowal1982/godot,Shockblast/godot,BastiaanOlij/godot,guilhermefelipecgs/godot,Zylann/godot,ZuBsPaCe/godot,akien-mga/godot,guilhermefelipecgs/godot,ZuBsPaCe/godot,sanikoyes/godot,Valentactive/godot,Shockblast/godot,Faless/godot,honix/godot,Faless/godot,Zylann/godot,firefly2442/godot,josempans/godot,firefly2442/godot,pkowal1982/godot,ZuBsPaCe/godot,guilhermefelipecgs/godot,DmitriySalnikov/godot,DmitriySalnikov/godot,DmitriySalnikov/godot,pkowal1982/godot,vkbsb/godot,vkbsb/godot,sanikoyes/godot,guilhermefelipecgs/godot,godotengine/godot,firefly2442/godot,honix/godot,pkowal1982/godot,ZuBsPaCe/godot