Add archive based updating mode (for buildbots)

Requires a modified updater since the manifest structure differs
significantly

It is not recommended to publish OBS with unsecured update sources,
i.e. either implement signing for downloaded resources and/or use secure
communications for downloading (preferably both)
Check updater integrity for archive based updating
Fix define usage
Fix typo in updater integrity check
Changes to update archives

Added preprocessor PropertyGroup for update archive macros
Fixed small bug in archive update code
Fix CUDA symbol loading
Remove accidental uncomment of updater defines
Fix copy&paste error in method declaration
Add plugin events for start/stop recording
Clarify callback semantics
Add plugin events for start/stop streaming

These complement the new start/stop recording events as they are called
as soon as a network connection is initiated/severed regardless of
previous encoder state
Refactored BitmapImageSource (moved core functionality into a new class - BitmapImage). Changed BitmapTransitionSource to use BitmapImage - implements #102
Add functions for accessing the current session log file to XT
Rename EnableProfileMenu to DisableMenusWhileStreaming

In case future modifications require more Menus to be disabled while
streaming
Move OpenLogFolder menu item to help menu

Leaving the localization strings unchanged for now for less confusion
on the translation site
Increase profile limit to 1000 and move magic constant to OBS.h
Add log file uploader implementation with GitHub Gist as upload target

As always, translation strings are open for discussion
Add UI for log file uploader

Also includes UI for opening specific log files directly from the OBS UI

On successful upload the resulting (non-API) URL is copied into the
clipboard and a message box signalling successful upload is displayed.
This should probably be expanded into a dialog with buttons to retry
copying the URL to the clipboard and maybe a text box with the URL
preselected.

Whether or not the upload URL should be cached (per log file) and reused
in case of duplicate upload (attempts) is still open for debate.
Fix Json escaping of quotes

Order is important for multipass escaping
Make sure we're throwing to log ugly stats stuff (division by zero case)