Prettify debug output

• Use console.info and console.error for qInfo and qCritical, respectively
• Add file name and line numbers, if available
• Use colored "Host" prefix instead of "From host"

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Before:

After (release build, screwed up the text color in this screenshot)

After (debug build)

Tested in both Chrome and Firefox. Chrome does not show the (i) prefix for console.info but otherwise shows the message fine.

For compatibility with older extension versions, the action remains debug and warning, so those messages are never lost.

@fvogt @davidedmundson