define release procedure

[PhilipDeegan]

what is done sometimes is to make a commit with all the controlled dependencies with particular versions, merge, then release master as a particular version of phare, then recommit back to tracking upstream after release

we should have a mechanism for controlling samrai and highfive at least

[PhilipDeegan]

versioning mechanism added via #887

todo, add RELEASE.md detailing release procedure

[PhilipDeegan]

I think the conclusion is

PR dep versions to master
Merge after builds pass
make release branch from master major or minor to be defined at that time
commit master back to dep master/HEAD

[PhilipDeegan]

dependencies to version during release

samrai https://github.com/LLNL/SAMRAI/
pybind https://github.com/pybind/pybind11/
highfive https://github.com/BlueBrain/HighFive/
cppdict https://github.com/LaboratoryOfPlasmaPhysics/cppdict