project layout added

Additional features

…rait

… for unit test cases for the components module

Implementation of mass_balance_check() and energy_balance_check() trait functions in blocks module

… external package pubchem.rs from crates.io

consolidated streams into 1 struct

Adding gnu license

…properties

I made the change as I to make sure that it is understood that the
ThermoState struct is used by the Streams within the flow diagram and
not by the blocks. The blocks (reactors, separators, etc) will contain
their own calculations.

On the other hand, the ThermoPackage may be used by both streams and
blocks

…pose

…mental std::autodiff is implemented into rust

fixed 'edition' for cargo.toml files

Gui backend integration

Implement property modules