Allow multiple circuits to be generated for a program with multiple operations

[DmitryVasilevsky]

If I click 'Circuit' code lens near an operation I get a circuit for it. If I select command 'Q#: Show circuit' it would draw a circuit for the entry point.
When I'm developing, I would like to see individual circuits for every operation in a file. I may not even have an entry point yet. And I may have some operations that will fail to generate a circuit, I don't want those to block the rest.
Make 'Q#: Show circuit' show circuit for every operation in a file. Maybe add a separate command to show it for the entry point.