re-add tags: make target
Allow all libraries to be overriden by settings.mk
Add new BC for variable densities in pressure FLOW_PRESSURE_VAR
Merge pull request #62 from dshari/FLOW_HYDROSTATIC_NEW

Add new BC for specifying hydrostatic pressure FLOW_HYDROSTATIC_NEW
Added entry for FLOW_PRESSURE_VAR to CHANGELOG
Merge pull request #63 from dshari/FLOW_HYDROSTATIC_NEW

Added entry for FLOW_PRESSURE_VAR to CHANGELOG
Merge branch 'master' into visc_mode_check