Add end portal support with support for choosing destination world

[AZFire1]

What would you like added? Support for viewing through end portals as well as nether portals.

I'd also love if this plugin entirely replaces MV-NetherPortals. To do so, I'd appreciate if support was added to have control of end portal linking between worlds like there is for nether portals. What this would effectively do is just know where end portals should shoot you within the worlds (like you currently have setup with your nether portal system). This also eliminates the need for me to have an entirely separate plugin for handling this basic feature.