Added replace parameter for setText

Requires https://github.com/admc/wd/pull/333 to be pulled first.

I also want to create a test for this in keyboard-specs.js but I can add that in another pull. 

Tested with the wd.js change and it works for me.
If we do this:

```java
params.getWithDefault("replace", false);
```

then it's a single check and only one method in the node server needs to care. The check exists in precisely one location in the code. The alternative is to make this param a requirement, change all invocations, and then crash if it's invalid/omitted.