Make dry run configurable using launchconfig

migrating from #34
## steps
1. `cs foo` where calling `foo --version` does something undesirable (like waiting for user input forever).
## problem

the installation process calls `foo --version` and does that thing.
## expectations

I would like to propose 2-tier solution to this using `launchconfig` file. Both of them involve adding an _optional_ section `conscript` to `launchconfig` as follows:

```
[conscript]
dry-run: false
dry-run-param: --something-not-version
```
### opt-out

The proposal is that we keep the existing behavior (run script with `--version`) by default, so existing happy conscript authors don't get sniped from the back. In other words, the new `[conscript]` section is totally optional.

If the conscript author just doesn't want to use dry-run option at all, they can opt-out by writing:

```
dry-run: false
```

Upon installation we don't do dry-run, and instead we print some warning saying that the jar's still not downloaded.
### `--help` instead of `--version`

Another scenario is that application does not support `--version`, but has some other harmless option already like `--help`.

```
dry-run-param: --something-not-version
```

This let's them customize to whatever. Again, if it's not specified `--version` is used.