Improved BTA! Signs

Improved BTA! Signs is a Better Than Adventure! mod that aims to improve signs in several ways.

• Adds two new sign variants, the hanging and wall hanging sign, placed on the bottom and side of a block.
• Allows adding text and changing the picture on the back of signs, each side can be dyed, glowed and locked separately.
• Allows displaying items and blocks to both sides of the sign when locked with a slimeball.

It also fixes two smaller issues with them.

• Removed the vertical offset the "Done" button has when editing an unpainted sign post.
• Removed the ability to dye sign text with dye items or the paintbrush when the sign is locked.