Add ability to handle multiple thread dump files

[kog]

I originally wrote JS-TDA to accommodate them, but took it out as I didn't see a need to do so. Still, might be handy rather than forcing people to open a new tab. You can drop a log with multiple dumps in it, which will (hopefully) display properly in the meantime.

Thoughts:

• Add a DIV under the dumps with a drag/drop area, a la 'no dumps' UI
• Maybe just add a plus button/DIV with a "append logs" or somesuch
• Should probably fingerprint each dump with a combination of file + time occurred to prevent collisions