Add conan project lockfile

[cassava]

This could improve reproducibility of builds by pinning specific versions of dependencies, instead of relying on Conan's dependency selection mechanism. Right now, I'm not sure how much work implementing this issue would entail. It might not be worth the benefit if it complicates the build and deployment more than it already is.

• Develop workflows for lockfiles:
  • Creating / updating lockfiles
  • Building the entire project
  • Building an individual Conan package
  • Overriding the lockfile?
• Update Makefiles to make use of lockfile
• Update documentation

Resources:

• https://docs.conan.io/en/latest/versioning/lockfiles.html

[cassava]

As it turns out, this does not really make sense in Conan v1. We should wait until we move to Conan v2.