feat: duplicate capture v1: display distance between two selected captures

[amesk3]

Description

In an effort to distinguish duplicate captures, this feature gets the distance between two currently selected features.

Issue(s) addressed
Duplicate verification issue.

• Resolves #issue_number
  Issue 781

What kind of change(s) does this PR introduce?

• Enhancement
• Bug fix
• Refactor

Please check if the PR fulfils these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

Issue

What is the current behavior?
N/A

What is the new behavior?
On /verify, when two selections are selected, Side Panel displays the distance between the two selections based off of their lat/lon. There is now label beneath the Select All and Select None buttons: Distance between selected captures: x.x m when two captures are selected

Breaking change

Does this PR introduce a breaking change?

Other useful information

This is the first part of addressing the duplicate image verification issue.

[amesk3]

Different scenarios of there being nothing selected, 2 captures selected, and more than 2 captures selected.

[nmcharlton]

There are a couple of tests that are now failing. Could you take a look? They may need updating to reflect the changes you've made.

npm run test

[nmcharlton]

Nice work!