Show information popup for missing dependencies

[szolo]

Steps to reproduce

1. Download default project from start.vaadin.com.
2. Import it to Designer.
3. Open any design, e.g. dashboard-view.js.

Actual behavior

Design is opened, but it is empty. Outline contains design structure.

Expected behavior

After design was opened it should be clear why it is empty.

IDE, Designer and OS version

OS: Mac OS X 10.14.5 x86_64
Browser: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_14_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/64.0.3282.24 Safari/537.36
Java: 11.0.2
IntelliJ: IntelliJ IDEA - 2019.1.3 - IC-191.7479.19
Designer: 4.3.1
Vaadin: 0.0.0

Intercom:

• https://app.intercom.io/a/apps/y0ueytrp/inbox/inbox/all/conversations/23012372705

Summary

Dependencies for design aren't installed until mvn package is not executed. For New Design wizard we're checking that node_modules folder exists. Similar should be done for opening already existing designs.

[szolo]

In Eclipse we already have a dialog, which is visible and suggests to execute mvn package. In IntelliJ IDEA we don't have it, because error log at the IDE bottom is used.
So, we need to adjust existing IntelliJ code a bit and show a popup message, because log record could be missed accidentally by the user.