auto the lambdas, removing the dependency on functional and improving readability.
Identation of folded expressions.
consistent #includes, some formatting
Uniformise remaining includes, formatting.
Define GravitationalParametre, remove auto from header.
Remove useless .cpp files.
Remove 'inline' from the header as it's redundant with the contents of the -body.hpp.
Merge pull request #22 from eggrobin/declutter-header

Declutter header
Merge branch 'master' into cleanup
Fix GrassmanTests following review by @pleroy.
Fix Quantities-body following review by @pleroy.
Fix Algebra-body following review by @pleroy.
const& argument.
Merge pull request #20 from eggrobin/cleanup

Cleanup
Merge branch 'master' into more-tests-for-R3Element