for the staggered coupling scheme

about getting the local solutions of an element.

Clang format run on near-the-header lines.

Happy New Year

 from the two classes of coupled term.

[Coupling] Changed the members of the coupled term,

 which only contains the solutions of the coupled equations.

pointer to StaggeredCouplingTerm

 coupled processes.

 for the staggered scheme.

See also "[PL] moved index computation to local assembler interface"
2d891b06 .