Ring buffer implementation

First stab at implementing a ring buffer. Now tuning should be done.
The statistics report causes jitters and can be deactivated by lowering
the output verbosity.

.gitignore

@@ -30,6 +30,11 @@
 *.out
 *.app
 
+# Build files with potential private info
+build/
+sdkconfig
+sdkconfig.old
+
 # =========================
 # Operating System Files
 # =========================
@@ -56,7 +61,6 @@ $RECYCLE.BIN/
 
 # Windows shortcuts
 *.lnk
-sdkconfig
 *.save
 libs/