Validate institution code in `/:inst_code` and `/:inst_code/home` routes

Routes

I Institution
R Resource
V View

• I /:inst_code
  • homepage#show
• I /:inst_code/home
  • homepage#show
• I /:inst_code/databases
  • catalog#index
• I /:inst_code/search
  • catalog#index
• IR /:inst_code/databases/:id
  • catalog#show
• IR /:inst_code/resource/:id
  • catalog#show
• R /resource/:id
  • catalog#show
• R /bookmarks/:id
  • bookmarks#show
• R /database/:id
  • catalog#show
• R /link/:code
  • link#show
• V /:view
  • welcome#index