Etabackend

**NOTE: ETABackend.exe should be downloaded mannually for ETA version <RC5.1**
1. upgrade Chromium
2. GUI now supports automatic (re)connecting to backend
3. zoom with Crtl + Scroll on main screen

RC4.9: ETA Real Time!!!
1. New API for run(self, cuts_params, ctxs=None, sum_results=True, iterate_ctxs=False, group="main")
2. Caching the compiled code
3. GUI fix for hiding the connection windows automatically
4. Disable multithreading for Websocket

RC4.10:
1. Better support for eta.incremental_cut()

RC4.11:
1. try fixing the crashing problem on windows 7

RC4: ETARealTime-ready.

rc4.0:
enable check-pointing for everything but reader or buffers

rc4.1:
1. the GUI will only "ETA running" when the actual analysis is running
2. fix the support of COINCIDENCE() and CLOCK()

rc4.2:
checkpointing now supports buffer for virtual channels and resorting

rc4.3 ~ rc4.6:
fix the crazy error of stackoverflow
WARNING: only two virtual channels are supported in these versions

rc4.7:
full checkpointing support.

rc4.8:
bug fix for simple_cut()