buildsystem: relax requirement on cmake version

Commit 73cc5089 (Using target_compile_features to specify C++ 11
standard) bumped the required cmake version, from 3.0 to 3.8, so
as to get the definition of target_compile_features().

However, target_compile_features() was introduced in cmake-3.1:
    https://cmake.org/cmake/help/v3.1/command/target_compile_features.html

And using cmake-3.1 is indeed sufficient to properly build.

As such, relax the minimum required version down to cmake-3.1,
so we can build on oldish, entreprise-grade distributions that
only have cmake-3.1 (or at least, don't have up to cmake-3.8).
Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

"V567 The modification of the 'position.chars_read_current_line' variable is unsequenced relative to another operation on the same variable. This may lead to undefined behavior."

 Added Support for Structured Bindings 

For further details, read https://github.com/nlohmann/json/issues/1388 and https://blog.tartanllama.xyz/structured-bindings/

Add a SFINAE friendly iterator_traits and use that instead.

Feature/add file input adapter

refactor unit test in case of throw, the fclose will not be called. using unique_ptr with custom destructor will ensure that

Add the possibility of using FILE * from cstdio library to read a file. This enable the possibility of using low eand device with this library.

Add the possibility of using FILE * from cstdio library to read a file. This enable the possibility of using low eand device with this library.

Link to issue #958 broken

recommend using explicit from JSON conversions

readme: fix typo