Move MoleQueue components to dedicated library

This allows Avogadro to be compiled without MoleQueue when desired.

Change-Id: I7168879a6334fad094d4e469b5b1555bbf872893
Removed redundant includes

Change-Id: Iaf45be25b3bef4a5ae7fd600e6044a599b9607f9
Merge branch 'refactor-molequeue'

Change-Id: I5bc5692ad6247e4db22d1c2b12fb5e480a378045