code: public VariableDecls declareVar(String bootiqueVariable) {
  		this.extender.declareVar(bootiqueVariable, VariableNames.toEnvironmentVariableName(bootiqueVariable));
  		return this;
  	}
docs: Declare an environment variable which is linked to the given Bootique variable, and has its name defined
  from the name of the Bootique variable.
  
  @param bootiqueVariable the name of the bootique variable.
  @return the Bootique extender.