Two cleanups: reserve and fill is equal to resize,
Wrote out ternary condition operator into if-else.

Since boost-1.61 (and also not in the std::optional)
optionals holding references do have some restrictions
and are difficult to use. In this special case
optional<PropertyVector&> is equivalent semantically
to a PropertyVector*. The pointer indicates that it is
not owning (contrary to usage of unique_ptr).

Thanks to Christoph pointing this issue out.

[SD-LIE] Common tools

[Mesh] searche boundary nodes in NodeSearch

Update PiecewiseLinearInterpolation functions

Integration order in project files.

Also fix the order in the initializer list.

Remove default value.

Takes around 15-20 minutes.