add architecture

ARCHITECTURE.md

+# Whirlpool architecture
+
+
+## I. Usage
+Whirlpool can be managed:
+- from desktop: `whirlpool-gui`
+- from REST API for developers: `whirlpool-cli API`
+- from command line: `whirlpool-cli`
+
+![](charts/usage.png)
+
+
+## II. Modules
+Whirlpool is modular:
+- 4 java modules: `server`, `client`, `protocol`, `cli`
+- 1 electron/react module: `GUI`
+
+`client` and `server` communicate through `protocol`.
+
+![](charts/architecture.png)
+

charts/architecture.md

+graph TD
+
+classDef ext fill:#faf9f9,stroke:#888,stroke-width:2px;
+
+GUI[Whirlpool-GUI] -->|rest CLI api|CLI[Whirlpool-CLI]
+CLI -->CLIENT[Whirlpool-client]
+
+CLIENT -->|websocket + rest|PROTOCOL{Whirlpool-protocol}
+
+SERVER[Whirlpool-server] -->|websocket + rest|PROTOCOL
+
+class DOJO ext

charts/charts.md

+Charts are generated from Markdown 
+using https://mermaidjs.github.io/mermaid-live-editor/

charts/usage.md

+graph TD
+
+classDef blue fill:#faf9f9,stroke:#888,stroke-width:2px;
+
+DSK(Desktop)-->GUI
+GUI[Whirlpool-gui] -->CLIAPI{cli-api}
+DEV(Third-party software)-->CLIAPI
+
+CLIAPI -->|rest|CLI[Whirlpool-cli]
+CMD(Command-line)-->|java -jar|CLI
+
+CLI-->CLIENT[Whirlpool-client]
+WALLET(Android)-->CLIENT
+class DSK,DEV,CMD,WALLET blue