File upload freshen up

[md8n]

• Remove a lot of the on* event handlers from the HTML back out to code, where they belong
• A few Ids changed/added into the HTML to enable the removal of the on* attributes
• Change those event handlers methods to be as simple as possible (no parameters), taking advantage of the way browsers behave to minimise duplication of event handler creation
• Change calls to SendGetHttp, SendFileHttp to use cmd instead of url as the values are NOT URLS but commands
• Some error handling around parsing responses
• Some checking around getting setting values etc. out of elements
• Minor clean up of app.js because the gulp linter complained about it
• Moved a few functions between files so they're closer to their actual usage