refactor: project structure (#9)

Split up project into multiple crates and use a Cargo workspace.

docs/sensor_data_shell.md

@@ -0,0 +1,29 @@
+# Sensor Data Provider Shell Scripts
+
+The [/linux/scripts](../linux/scripts) directory contains some proof-of-concept Linux shell scripts.
+
+CPU and memory usage are written into a sensor data source text file that can be used by `asterctl`.
+
+```
+./cpu_usage.sh -h
+Simple PoC script to periodically write the CPU usage into a sensor text file.
+
+Usage:
+./cpu_usage.sh [-r REFRESH] [-s SENSOR_FILE] [-t TEMP_DIR]
+
+  -r REFRESH     refresh in seconds.  Default: 1
+  -s SENSOR_FILE output sensor file.  Default: /tmp/sensors/cpu.txt
+  -t TEMP_DIR    temporary directory. Default: /tmp
+```
+
+```
+./mem_usage.sh -h
+Simple PoC script to periodically write the memory usage into a sensor text file.
+
+Usage:
+./mem_usage.sh [-r REFRESH] [-s SENSOR_FILE] [-t TEMP_DIR]
+
+  -r REFRESH     refresh in seconds.  Default: 5
+  -s SENSOR_FILE output sensor file.  Default: /tmp/sensors/mem.txt
+  -t TEMP_DIR    temporary directory. Default: /tmp
+```