Syntax checking / linting for console expressions

[outoftime]

If the coder types an expression into the console that is not syntactically valid, we should recognize that and provide good, human-readable feedback rather than sending it to the preview frame be evaluated and throw a generic syntax error.

We can probably also do some very light linting here, probably a small subset of the rules we use for linting project JavaScript code.

Very closely related to #1264

[outoftime]

@omardeleo writing down the sequencing we discussed on Tuesday:

1. Add a new logic (docs here) that consumes the EVALUATE_CONSOLE_EXPRESSION action, runs the expression itself through the JavaScript validator, and then prints the result to the Chrome console
2. Add a new validationState property to the ConsoleEntry record, whose values are an enumerator of pending, valid, or error. The default state should be pending
3. Add new actions, CONSOLE_ENTRY_VALIDATION_SUCCESS and CONSOLE_ENTRY_VALIDATION_ERROR; update your logic to dispatch the appropriate action given the outcome of the validation in step 1.
4. Update the console reducer to consume the actions from step 3 and update the validationState and error properties of the entry in question.
5. Update the logic in the PreviewFrame component to only evaluate console entries whose validationState is valid (note that you will need to filter both the previous collection and the current collection, to find entries that were not previously valid but now are)
6. Update your logic to prepend all valid entries from console history to the current entry before passing it to the validator. You will only want to include entries that:

• Have a validationState of valid
• Have a compiledProjectKey matching the current one