Preparations for release v1.2.0

[cnpetra]

hiopBBpy related updates (add items as needed)

• - short description of solver in README.md and pointers to additional doc: installation, usage, interface, parallel runs (T)
• - user manual update (as per in-person discussion) (T)
• - logging
• - merge PR Update IPM NLP solvers to be aware of weighted spaces #710 (C)
• - make Ipopt optional, including the build system (NY)
• change the updated date in pdf. some references are missing in user manual (C)
• revisit user manual (recent additions): bump ver number, capitalizations, etc.
• test non-MPI build, including derivative checker (C)