Add README for ATxConfigTest.

ATxConfigTest/README.md

+# AutoTx Configuration Validator
+
+The `AutoTxConfigTest` tool can be used to validate a set of configuration files
+and print a summary to the console.
+
+## Basic Usage
+
+By default, configuration files are expected to be in the same directory as the
+`AutoTxConfigTest` executable. In that case simply run the tool like this:
+
+```
+.\AutoTxConfigTest.exe
+```
+
+## Advanced Usage
+
+Instead of checking the config files in the directory of the executable, any
+other path can be specified as the first parameter when running the
+configuration validator, e.g.
+
+```
+.\AutoTxConfigTest.exe C:\Temp\new-config\
+```
+
+This also works with UNC paths, like
+
+```
+.\AutoTxConfigTest.exe \\some.file.server\share\new-config\
+```
+
+To increase the log level of the parser, a second parameter can be specified as
+either `debug` or `trace`:
+
+```
+.\AutoTxConfigTest.exe  C:\Temp\new-config\  trace
+.\AutoTxConfigTest.exe  .  debug
+```
+
+## Exit Codes
+
+A valid configuration will result in exit code `0`, an invalid in `-1`.
\ No newline at end of file