Develop a plan and assign tasks for moving to C++17

[rhornung67]

Add tasks related to this here....

• Return type deduction instead of trailing return syntax (C++14)
• Fold expressions
• contexpr if
• CTAD
• Non-type template parameters declared with auto
• constexpr lambda
• Lambda capture this by value
• Inline variables
• Nested namespaces
• Structured bindings
• Initializers for if and switch
• Attributes
• Investigate simplify recursive camp::num template instantiations with fold expressions
• Investigate simplifying RAJA kernel with fold expressions

See also:

• C++17 Remove CUB and rocPrim TPLs #1540