Changelog for BuildCraft 6.4.7

Improvements: * Minor improvements to fluid pipe extraction, fillers and pipe icon handling (asie)

Bugfixes: [#2564] BC pipes lose liquid when different fluids mix in them. (asie - thanks MatthiasM2 for the 6.4.x workaround) Combustion engine not updating the fuel RF/t value (asie) Error while loading robot resources (hea3ven) Invalid engine rendering size (asie - introduced in 6.4.6)