Bugfixes.

Created by: PJB3005

RCD & RPD bugfixes:

• Fixed calling of select() from the base RCD class.
• Fixed pipe layer adapters in the RPD. Fixes #6318 (closed).
• Made pipe layers stay when you switch beween pipe schematics.
• Fixed the pipe layer selector not loading if you didn't select the straight pipes first.
• Fixed bent pipes not having a correct director selected initially.
• Fixed disposals pipes having an (unusable) layer selector in the RPD.

Silicate sprayer fixes:

• Silicate sprayer now says if it's out of silicate, Fixes #6367 (closed).