feature request: moment-carrying nodes

[ruzko]

Thank you for writing this program, I love it

What: please add three features:

1. Option to make a node stiff / carry moment between members
2. A fourth support type, which carries moment / is stiff
3. Moment as a load type

Why: Yesterday I had to determine displacement in a system where a load was applied between two truss nodes. i.e. on the span of a member. This proved difficult, and I ended up doing it manually using the unit load method. Today I had to determine displacement in a truss system containing moment carrying corners / stiff corners, as well as a stiff support.

I think both of these use cases could be covered if the requested features are implemented.

As a side note, I use Linux and would love to see cross-compatibility, either as a linux native program or through wine.