disabled allowFlowReversal in pumps
fixed DHW implementation:
singular system because of pressure boundary condition
used idealsource instead of pump to reduce number of equations
using pipe_heatport to set output temperature

added example
added DHW unit test results
Merge branch 'Annex60' of github.com:open-ideas/IDEAS into Annex60
re-enabled flow reversal in pumps: c209b3907fd62cde3b5
added reference results for unit tests damien