Finish sign implementation

[Sandertv]

The sign implementation at feature/signs requires some minor changes to the way the rotation + wall/standing is structured. With some other small changes this should be ready to be merged into master.

[Sandertv]

Going to postpone this to the start of v0.2.0. I don't have enough time to finish this in v0.1.0 and definitely not enough time to make sure it all works properly by the end of the month. v0.2.0 is a safer time to release.

[Sandertv]

Signs are quite far in now. The feature/signs branch has most of the implementation ready. There are a couple of things left to do:

• Verify that only the owner can edit a sign.
• Look up what colour codes (RGBA) correspond to which dye colours.
• Figure out exactly what glow ink does to the text. (Seems like it just turns up the A channel of the RGBA to maximum?)
• Maybe have some sort of event for sign editing, including dyeing.