[#285] Init messages fix and graph load when init repo

[dylanfu]

Resolves #285.

• Adds more meaningful messages when trying to create a repo that already exists.
• Also loads repository into the main panel after creating a new repository (graph, file, header).

Test 1:

1. Create a new repo
2. Check graph and associated file and header variables load.

Test 2:

1. Create a repo in a directory that a repo already exists/ or create a repo in the same directory twice.
2. Popup message regarding this should show up.
3. Check graph and associated file and header variables load.