HighPassFilterAction: attempt to clarify "revised" behavior

In both comments in the implementation and the description in the GUI, try to
emphasize that in StoreRevised mode, the revised image gets set to the filter
residual, i.e., the difference between the high-pass filtered data and the
original data, i.e., the data as processed with a low-pass filter.
src/gui/strategyframes/frequencyselectionframe.h: add this

This adds a GUI editor for the FrequencySelectionAction. It required adding a
public getter/setter for the "clipDown" parameter to this action.
Merge commit '71e6773c5bb3135ef1b6704dd9342c9d75e00eaf'
src/strategy/actions/foreachpolarisationaction.h: _changeRevised to true

Without setting _changeRevised to true, the "Background" image in the rfigui
never gets updated if the strategy includes a ForEachPolarisationAction. Without
this it's very hard to understand if the iterative algorithm is working.
BUILDHACK: compat with NRAO casacore
BUILDHACK: CMakeLists.txt: avoid LD_LIBRARY_ foo with rpath magic
BUILDHACK: CMakeLists.txt: link casa_lattices; not sure if needed, actually
UPSTREAMABLE: src/msio/scalarcolumniterator.h: greater API compatibility

Some versions of casacore replace the ROScalarColumn class with a
simple #define to ScalarColumn, which turns the overloaded method into a
compile error. Avoid this problem.
CHATTER: src/aoflagger.cpp: uniform spacing of percentage output
CHATTER: src/aoflagger.cpp: progress reporting all on one line
CHATTER: src/strategy/actions/baselineselectionaction.cpp: quieter
CHATTER: src/aoflagger.cpp: no long startup message
CHATTER: add 'quiet' option
BUILDHACK: more compat with NRAO casacore