resolves #44

What this PR does:

Adds functionality to enable retrieving CodeSystem data from the database and displaying it in the UI

Search input

• Send a POST request to submit form data from the SearchBar component
• Add a new route and handler for above request
• Adjust the HTML layout to include the data from the dropdown menu in the form

Display search results

• When results are returned successfully, update the url to show the search type and search term (e.g. /search?type=code_system&input=1.0.3
• Display a basic error message if no rows are returned from the db lookup
• Dynamically show/hide/disable the pagination buttons and download button based on results returned
• Display the first five result rows in a table:

What this PR does NOT do:

• Functionality is currently limited to CodeSystem lookup by OID or partial OID
  • Changing the dropdown menu input will not affect which db tables are queried
  • Name/text based search is not included; results are only retrieved with a CodeSystem OID
  • A partial OID can be entered and will be matched from the string start (e.g. 1.0.3 will return 1.0.3166.1 but won't return 2.1.0.3)
• Full pagination is not yet implemented; the first five results returned will display in the table but page buttons do not currently work
• Related data (e.g. CodeSystem Concepts and ValueSets related to a given CodeSystem) are not yet returned/displayed in the UI