Gnu install dirs

See merge request osdu/open-vds!5

Install a -config.cmake export file with openvds, so downstream users
can find_package() if using cmake.

Because openvds_objects and jsoncpp are actual dependencies, they must
be in the export set. In the case of jsoncpp it must also be installed,
at least for now.

GNUInstallDirs is the standard package in cmake to decide (and
configure) install directories, and is aware of certain distro
preferences like REHL's lib64.

Replace the hard coded lib/bin paths with the dynamic ones provided by
GNUInstallDirs.

Changed the isReadWrite parameter to createVolumeDataPageAccessor to be an AccessModeEnum with an AccessMode_Create option so we can handle ProduceStatus better (passing this accessmode changes the produceStatus of the target layer to ProduceStatus_Normal).

Build python bindings optionally (default on)

See merge request osdu/open-vds!4

It's useful to be able to build the core parts of the project without
having to bother with the python runtime, dependencies, and even build
time.

Add build framework for python extension

See merge request osdu/open-vds!3

Implement the minimum required framework to build a pybind11 [1]
generated python extension. The approach is based on various Equinor
projects [2].

The python building relies on high-quality export files, both from
install(EXPORT) and export(TARGETS) for both installed and build-dir
copies of openvds.

In short, the approach is to build the python code with python tooling,
integrated with the root cmake project through a custom target.

[1] https://pybind11.readthedocs.io/en/stable/
[2] https://github.com/equinor/ecl3

Use atomic<int64_t>, not atomic_int64_t

See merge request osdu/open-vds!2

It seems like libstdc++ for gcc<7 does not include the alises for
atomic_intN_t. A reasonable workaround is to use the actual type
directly, instead of the alias.

Set correct number of samples for inline/crossline dimensions. Explicitly call commit() to write back remaining pages at the end.

Implemented createPage in VolumeDataPageAccessor to make it possible to do low-level brick-by-brick writes. Fixed various bugs related to writable pages.