Experimental ESXi Support

Added an experimental build ESXi MachineManager support.

Supports snapshots, power state, and networking.
status bug in esxi

status bug
Update modules/machinemanagers/vmware_esx.py
Check for Word Viewer if Word not found
Merge pull request #77 from chort/development

Check for Word Viewer if Word not found
Matching Yara signatures on all files
Updated Yara details in HTML report
Added arguments to DLL package
Updated HTML template
Updated HTML report template
Fixed empty Yara sigs in dropped files
Fixed break words on HTML report
Update screenshot.py

Changed how the difference between two screenshots is determined. It uses root mean square (code copied from: http://code.activestate.com/recipes/577630-comparing-two-images/) to determine how much it has changed. This overcomes the problem of a blinking network activity icon or blinking cursor from generating multiple screenshots.
Fixed bug
Catching MemoryError exception on malware upload
Change default dates in database.py to callables

This does not affect submit.py, which creates a new Database() each
time it is run, but web.py and api.py both create a single Database
on startup, so previously all tasks submitted via these methods used
the date of startup rather than the actual submission date for Tasks.
Merge pull request #81 from MITRECND/date_fix

Change default dates in database.py to callables
Merge pull request #78 from carbito/patch-2

Changed how the difference between screenshots is determined
Added comments
Added other buttons to click