(towards) Aero Thermo Elasticity

[pcarruscag]

Proposed Changes

This allows one to define a triple physics simulation where structural displacements due to fluid forces are also applied to a heat transfer solid domain
example.zip
but where the temperature of that domain does not influence the elastic response (for now),

PR Checklist

• I am submitting my contribution to the develop branch.
• My contribution generates no new compiler warnings (try with the '-Wall -Wextra -Wno-unused-parameter -Wno-empty-body' compiler flags).
• My contribution is commented and consistent with SU2 style.
• I have added a test case that demonstrates my contribution, if necessary.
• I have updated appropriate documentation (Tutorials, Docs Page, config_template.cpp) , if necessary.

[WallyMaier]

Thanks for the work, this definitely looks alot cleaner. LGTM