Update dev instructions to use starter site

[joshdentremont]

Instead of make local, recommend that we use make starter for dev installs

Purpose / why

Starter seems to be the recommended way to install now, and is easier to work with for new installs

What changes were made?

install instructions changed from make local to make starter

Verification

Create a new site with make starter as described in the changed documentation.

Note: make starter does not currently allow installing from an existing codebase without a few extra steps not described here, but I have a PR (Islandora-Devops/isle-dc#336) that will allow it to. If necessary I can update these docs to include the extra steps, but ideally that PR would go through first so that won't be necessary.

Interested Parties

• @Islandora/documentation

Checklist

Pull-request Reviewer

Pull-request reviewer should ensure the following:

• Does this PR link to related issues?
• Does the proposed documentation align with the Islandora Documentation Style Guide?
• Are the changes accurate, useful, free of typos, etc?

Person Merging

The person merging should ensure the following:

• Does mkdocs still build successfully? (This is indicated by TravisCI passing. To test locally, and see warnings, see How To Build Documentation.)
• If pages are renamed or removed, have all internal links to those pages been fixed?
• If pages are added, have they been linked to or placed in the menu?
• Did the PR receive at least one approval from a committer, and all issues raised have been addressed?

[ysuarez]

We will be waiting this PR to be merged before we do this one
Islandora-Devops/isle-dc#336

[seth-shaw-asu]

@ysuarez, Islandora-Devops/isle-dc#336 was merged. Is this good to merge now?