Merge pull request #2017 from AEnterprise/6.1.x

fixes for construction marker
fixed deadlock when getting properties from main thread
Merge branch '6.1.x' of github.com:BuildCraft/BuildCraft into 6.1.x
fixed style
Merge pull request #2018 from AEnterprise/6.1.x

fix MJ->RF migration with blocks that where already in the world
Update README.md

Added a section on contributing regarding maintenance and residual bugs.
Fixed wood pipe accepting energy from other pipes, following RF migration.
Part of #2016.