Improvements on Aggregate's installer workflow.

[kkrawczyk123]

Software and hardware versions

Windows/Linux/macOS, Aggregate v2.0.x, Java vx.x.x, ...

Problem description

I think that UI of installer workflow should be improved as on Ubuntu there are some weird elements visible like on attached screenshot:

And also there is no way to change the default value of port 8080, I have got an error message when change it to 18080 and I was not able to continue the work:

All other improvements idea are welcome!
cc @ggalmazor and @yanokwa

@opendatakit-bot label "needs discussion"

[ggalmazor]

The port issue is due to a bad validation regexp, which expects a port with just 4 numbers. Port 18080 will fail the regexp test and prevent completing the installation

[kkrawczyk123]

It would be also good to consider changing the order of MySQL and PostgreSQL on the list and selecting PostgreSQL as default. ?