Create Application Header

[minjungb]

What's this PR do?

this is the application header component. -renamed and cleaned up application header files

Where should the reviewer start?

applicationHeader.html _cbp-appHeader.scss

How should this be manually tested?

check to see if applicationHeader.html is displaying properly and the dropdown is functional in both desktop and mobile views.

Any background context you want to provide?

the dark background overlay and animation for when mobile nav is opened in tablet view still needs to be implemented.

What are the relevant tickets?

Screenshots (if appropriate)

Questions:

• Is there a blog post?
• Does the knowledge base need an update?