Implementing new PROJ API

See merge request !16

Updating FindPROJ.cmake to stick to the old PROJ4 interface for as long as it is available, and switch to PROJ otherwise (version 8.0.0 or higher of libproj). This because we use a function that was only introduced in version 8.0.0.

Now the user only has to enable PROJ and cmake will find out if either
proj4 or proj is installed on the system, then compile and link with the
proper version of the library.

Using c++11 regex, if all the matching keys are build such as {some
prefix}{some integral number} then they will be sorted by natural
numerical order (ie 10 comes after 9 and before 11). If not, purely
alphabetical order is used (so STATION10_a comes before STATION2_a).

The code between getValues() and getKeys() will not be unified.

More c++11, more consts, improved readability and fixed a linking error
on some platforms

Now it is possible to set Meteo1dInterpolation::WINDOW_SIZE to zero, this
internally sets ENABLE_RESAMPLING to false.

Fixed the writing of varying number of parameters in SMET

See merge request !15

Handling varying number of parameters over a large time range has always
been tricky, as it was necessary to figure out the exact list of
parameters before allocating the memory as well as before writing the
data. The memory allocation part was done in a previous commit, but the
SMET plugin did not manage to reliably write such data.

This is now fixed, knowing that the parameters are now writen in
alphabetic order.

ERA5 request: code usage guide

See merge request !12

Feature/ci without manual zipping

See merge request !13

(see similar commit in Snowpack)

This reverts commit 0b9fc952.

It takes a new argument in order to still accept ".." as this is useful
when importing ini files in operational systems.

This has always been a pain to handle, when new parameters appear or disappear,
since plugins such as SMET need to know before starting writing data out which
parameters there will be. Now a new static method has been written to unify the
meteo parameters over a whole MeteoData vector. This comes with some performance
cost but this should mostly impact vectors where the number of parameters
changes.

Doing the "local value has priority" in a different way has allowed to define a
key as a reference to a key that is imported or even defined with a call to
addKey() (that has to be performed before parsing the file that refers to it).
This gives more flexibility when writing ini files that must be relocatable
based on environment variables of a additional key such as "CWD", for example to
be used in sandboxed environment.

It is either coming from the git version (if the "version from git"
cmake option has been selected) or from the major/minor/patch versions
(which itself is either hard coded in the CMakeList or set from
evnvironment variables).

era5 request update

See merge request !11

This provides an up to date code example to download ERA5 netcdf files
for use by the Netcdf plugin

Improvements for tests and pipeline

See merge request !10

This reverts commit 995064bf.