Create bundle parameter or credential from selected value

[itowlson]

The user should be able to select a block of text in the active document (e.g. exec command, ARM template, etc.) and choose a 'turn this into a parameter' command. This should create a suitable parameter in the porter.yaml. Ideally, it should also modify the source location to reference the parameter, but that may be tricky without knowing the source location syntax and how the parameter is passed into the invocation image - but it will at least be possible if the source is the porter.yaml file itself.

It should also be possible to turn the value into a credential instead of a parameter.

[itowlson]

Example from @squillace: "Usually if I'm given an bash script that has "$INSTANCE_NAME" in it, I want to highlight "INSTANCE_NAME" and then hit the command sequence. We might even go so far as to assume that IF the name of the selection is usually a variable/env var, THEN we might actually not only create the dummy param for them but also replace their selection with the correct {{bundle.parameters.<slelected value>}} form as well. But I'd take that as a second step, not the first."