[docs] Keep track of the minimum supported versions of our dependencies in a centralized location

[SergioRAgostinho]

Is your feature request related to a problem? Please describe.

Meta problem. Often we rely on maintainers and contributors memory to know what are the current minimum supported versions of PCL's dependencies, be it compilers, tools or 3rd party libs. Each person might know a few but there's always a chance that it is unknown to all.

Context

During an issue discussion or review process it happens frequently that a user/contributor/maintainer will not really be aware what minimum versions PCL is supporting.

Expected behavior

I would like to have all this info centralized somewhere.

Current Behavior

We're relying on everyone's memory. :)

Describe the solution you'd like / alternatives you've considered

A dedicated CMake file - would allow for a nice configuration/substitution directly to the docs and other places in our code. Currently, the integration with tutorials is not really viable because read the docs is using the bare folder without running any configuration. README.md - easy for users to see but hard to update other places of the source tree which might want to rely on this info

[larshg]

Could it be made so that a CI would run with lowest / highest versions like once every week/month. Just to occasionally test that nothing broke :)

[kunaltyagi]

The funny thing is minimum version of some software is less than the ones available on the oldest CI. PS: Does anyone know the minimum eigen version for PCL? 😆

Eg:

• FLANN (I'm sure it works with 1.7 now, but minimum available is 1.8 on 16.04)
• Boost (1.58 doesn't have many big changes compared to 1.57 or even 1.56)

[SergioRAgostinho]

I think we don't need to be that strict with what is actually minimum. It's more, we'll ensure support from version X up to Y of this library. Versions above and below might still work, but are untested.