Avoid using unopened files.

When many channels are selected for recording a race condition can cause a crash by writing to a file that has not been opened yet.
Added Open Ephys data files to .gitignore
Added files for RHD2000 DataThread
GUI can now communicate with RHD2000 eval board (but no data transfer yet)
Updated RHD2000Thread; thread streams data at up to 30 kHz, but the samples still look like junk
RHD2000Thread is working for 32 channels
Removed check for multiple Intan Boards in ProcessorGraph
Merge remote-tracking branch 'upstream/master'