Cherry-picking and editing commit 4f7e4f66 (bugs fixed in stability corrections)

Added two new keys to control the inflate/deflate feature

With SNOWPACK::INFLATE_ALLOW it is possible to turn on/off inflate/deflate both
in operational and research mode (note that by default, it is turned off in
research and on in operational). If SNOWPACK::INFLATE_INFO is set to true, then
a message is printed every time inflate/deflate changes the mass balance.

Otherwise, the OSWR fields in the exmaple smet files have been renamed as RSWR.

For the operational Snowpack, we want to allow more iterations in the solver for higher chances of convergence

There was a problem on osX that it would only compile against the SDK version of the system doing the build. As I was often lagging way behind, this was not a problem but now that I've updated to the latest version, older versions of osX could not run the binaries. Now compatibility with SDK version 10.13 (High Sierra) is enforced and cmake is required to be at least 3.0.2.

Unfortunatelly, the results of the tests still depend on the machine it is running on... Moving to a new CI server means new reference files (although these are now much closer to the results I get on my own desktop).

Improving the FindMeteoIO.cmake and FindLibsnowpack.cmake: it now gives priority to installations close by and should better handle when it is not found

TRying to only perform ctest_memcheck on the snowpack binaries, not on the bash scripts that evaluate the energy balance, etc

Striving to make all cmake files as similar as possible between the different projects. Moreover, there was a bug leading to some gcc DLLs not to be packaged on Windows. They are now statically linked.

Similar handling of Inishell as in MeteoIO but on osx, no error message is returned so the other components can still be bundled

Snowpack's version has been bumped to 3.6.0. The linker flags for RPATH were still a little wrong: GNU ld does not support @executable_path but $ORIGIN, so now a test for the platform is performed in order to use one or the other variant. Inishell-ng is now bundled if the "BUNDLE_ALL" option is set to true in cmake and the local installation of niviz has been disabled (since it does not run without a web server in its current version).

Now ACDD metadata is supported in SMetIO for timeseries. It will be refined in the next commits though

Now soil evaporation model is configured with an new SNOWPACKADVANCED::SOIL_EVAP_MODEL key (as in dev branch). In addition, the soil thermal conductivity computation from fitted data can now be bypassed with another new SNOWPACKADVANCED::SOIL_THERMAL_CONDUCTIVITY key. Default behaviour is unchanged. Key descriptions are at the end of Snopack constructor (wnowpackCore/Snowpack.cc)

Minor optimization so we can call TechSnow::preparation() even when there is not enough snow for grooming (and it should remain efficient).

The TechSnow class can not be static anymore: reading config keys at every timestep is very inefficient, so they have to be read once in the constructor and saved for all subsequent calls.

The SNOW_PREPARATION key has been renamed into SNOW_GROOMING because it was conflicting with the snow production in Alpine3D

Moved all the TechSnow keys into a new TechSnow section (so these keys don't end up into a SnowpackAdvanced section and can be shared with Alpine3D)