Update dds-agent-cmd docs

dds-agent-cmd/README.md

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+# dds-agent-cmd
+
+Send commands to agent. **UNIX/Linux/OSX**
+
+## Synopsis
+
+```shell
+dds-agent-cmd [[-h, --help] | [-v, --version] | [command, --command arg] | [-s, --session arg]] {[getlog arg] {[-a, --all]} | [update-key arg] {[--key arg] | [--value arg]}}
+```
+
+## Description
+
+This utility allows to send commands to DDS agents.  
+For the currently available commands see [Options](#options)
+
+## Options
+
+* **getlog** *arg*  
+Download all log files from active agents. All files from agents' working directories with the extension `.log` will be tar/zip'ed into a single file and downloaded on DDS commander server machine into the directory specified by `server.log_dir` DDS configuration option and placed in the subdirectory "agents" (default:`~/.DDS/log/agents`)  
+Usage example:
+
+  ```shell
+  dds-agent-cmd getlog -a
+  ```
+
+* **update-key** *arg*  
+It forces an update of a given task's property in the topology. Name of the property and a new value should be provided additionally (see `--key` and `--value`)  
+Usage example:
+
+  ```shell
+  dds-agent-cmd update-key --key mykey --value new_value
+  ```
+
+* **--key**  
+Defines the key to update
+
+* **--value**  
+Defines a new value of the given key.
+
+* **-a, --all**  
+Send command to all active agents.
+
+* **--s, --session** *arg*  
+DDS Session ID.