Update WebAdmin

All files have been updated to the latest version off the new WebAdmin
look.
Update guest.html
Update style.css
Update (original).html
Update login_template.html
Update temp.html
Update login_template.html
Update login.css
Update style.css
Update template.lua
Update login.css
Added IsBiomeVeryCold() and IsBiomeCold() functions.
Added new biomegen: Grown
Added a missing header to CMakeLists.
Fixed a copypasta error in cIntGenAddToOcean.
BioGenGrown: Smaller biomes, add land to map center.
IntGen: Attempt at fixing Linux compilation.
Removed too advanced C++11 features.

We need to keep gcc 4.6 compatibility; these features were not implemented in that version yet.
cIntGen: Added a virtual destructor.
Update guest.html