Clarify requirements for setting up Oskari development environment

[ismogis]

I'd have some suggestions to improve the clarity of the requirements on the page that guides developers through setting up the development environment (https://github.com/oskariorg/oskari-documentation/blob/develop/3%20Setup%20instructions/00040-SetupDevelopmentEnvironment.md). The instructions are quite clear, but a few adjustments would make them even easier to follow.

1. The database is missing from the list of requirements. It would be helpful to include a link to the page 00020-SetupDatabase.md.

2. {jetty.base} is listed as a requirement. This can be misinterpreted as needing to set up the environment variable called 'jetty.base'. If I understand correctly, the requirement is actually for the unzipped Jetty bundle.

3. The download link for the Jetty bundle is not working.

4. Under the section "Fetch Oskari-server...", it is mentioned that Git is only mandatory when contributing changes to Oskari. This should be mentioned earlier in the Requirements section.

[ZakarFin]

Thanks! Good points. The download takes you to the download page when this is shown on oskari.org, but it doesn't really work when viewed on GitHub and is misleading as such. Maybe we should include the domain just so it works as expected when viewed on GitHub.

This page is more about setting the development environment for building the code. That doesn't require the database, but then again we should review what would make sense to list here. Definitely the jetty.base reference is misplaced and should not be part of the requirements list.

The git part is a bit difficult. Should we just reference to getting the code "some way" as in downloading the zip from GitHub or using git to get the code or just mention that version control is good and you should use it :) Probably needs some updating as well though.

[ismogis]

@ZakarFin I would prefer that this page also included guidance on how to run the application in a development environment. It could, of course, simply provide links to resources like setting up the database.

[ZakarFin]

When you read this as a page on the new Oskari.org site (found in oskari-documentation-site repo next to this one) everything under a folder like "3 Setup instructions" is shown as one page and the numbers on the filename prefixes are used to sort them so the order the pages are concatenated make sense. We might need to rethink how we store these on GitHub if we want to make both read similarly and maybe concatenate the source to one page as well to make it work better on both. Then again I'm not sure if that would break how the navigation for the documentation is created on the new site. It would be nice if one could follow the documentation from either source, but we might need to compromise to get it working nicely on at least one of these.