Week 4-BN: start OpenOCD from the BN console in the background; gitignore helper logs

Step 10 now shows starting the debug server from the console: pkill/taskkill any
running OpenOCD first, then Popen debug-server.sh(.ps1) with BP_ADDR and output to
openocd.log so the console returns immediately. Verified: Popen returns in ~6 ms,
log shows 'Startup breakpoint at 0x10000234' + 'Listening on port 3333'. Ignore
openocd.log/flash.log/build.log.

.gitignore

@@ -72,3 +72,9 @@ svg-to-pdf.ps1
 ehthumbs.db
 Thumbs.db
 
+# Logs written by the Binary Ninja console helpers (build / flash / OpenOCD)
+openocd.log
+flash.log
+build.log
+build-flash.log
+