Change image link (now relative)

https://github.com/blog/1395-relative-links-in-markup-files
A horizontalOffsetPlane for things like train tracks and whatever.
Merge remote-tracking branch 'movingblocks/develop' into smallBugfixes
Terasology. New block family. Fences, rails and lader as bonus
Adds various new rendering related features and tweaks.

- Adds real refractive surfaces (third render pass for solid chunks - yey).
- Renames various shader parameters and adds many new properties
- Removes faked refractive water surface and adds a new config option to enable water refraction
- Tweaks shading of ocean waves on "Insane"
- Some more things I forgot...
Added support for a dependencies list in mod.txt. This informs the build, the projects created for mods, and the selection of modules ingame.
Also improved generation of mods by the build script. If you add a new mod to settings.gradle and gradlew, then the mod directory and a skeletal mod.txt will be generated. Additionally the task 'mods:mymodname:createSkeleton' will generate a full directory skeleton with folders for all asset types and source code.
Merge branch 'develop' of https://github.com/MovingBlocks/Terasology.git into develop
Fixes that activating the "Insane" graphics quality setting without "ANIMATED_GRASS" lead to shader compile errors.
Packs some of the many chunk shader parameters into Vector4s and tweaks ambient lighting and refraction water intensity.
Tweaks refraction intensity and adds that various opaque renderables (like items and small blocks) get rendered to the refraction FBO.
Merge #438 from @AWFeldick first even though it also exists in #446 :D
Merge #446 from @small-jeeper for auto-adjusting fences, rails, and a ladder!
Merge #444 from @mkalb to make an image link relative
Tiny bit of cleanup/commenting
Fix for rotated blocks appearing darker (caused by floating point errors)
Merge branch 'develop' of https://github.com/MovingBlocks/Terasology.git into develop
Fixes shader compile error / warning and extends debug information output on compile errors or warnings (line where the error is located is copied from the assembled shader source to the log / output window).
Backported audio system improvements from multiplayer fork. Volume controls and null audio system now supported.
Merge branch 'develop' of https://github.com/MovingBlocks/Terasology.git into develop
Improvement to previous Ambient Occlusion fix in chunk tesselator.