Add support for url prefix

[fr3nch13]

We want to be able to run the hxtool behind a nginx reverse proxy along with other tools, and need to have it run off of a 'sub folder'/url_prefix. like https://localhost:8000/hxtool

I updated this app to add support for url_prefixes.

• It also updates all hard-coded urls in templates to variables.
• For some javascript files, the urls are passed to the functions, instead hard coded as well.
• I also broke the core app out into a separate Blueprint so it could support the url_prefix as well.

I was able to test it locally on my laptop, but I haven't thoroughly on a server with proper access to fireeye (login, api, etc).