Add thematic overview of CPROVER directories

Author: Charliemowood

doc/architectural/cprover-architecture-overview.md

@@ -52,6 +52,57 @@ interpreted) are named with `_typet`. For example `ui_message_handlert`
 rather than `UI_message_handlert` or `UIMessageHandler` and
 `union_typet`.
 
+# Overview of CPROVER directories
+
+- language front ends
+
+  * ansi-c
+  * cpp
+  * langapi
+  * jsil
+
+
+- static analysis
+
+  * analysis
+  * pointer analysis
+
+
+- utilities
+
+  * big int
+  * json
+  * xmllang
+  * util
+  * miniz
+  * nonstd
+
+
+- tools
+
+  * cbmc
+  * clobber
+  * goto-analyzer
+  * goto-instrument
+  * goto-diff
+  * memory-models
+  * goto-cc
+  * jbmc
+
+
+- goto-programs
+
+  * goto-programs
+  * linking
+
+
+- symbolic execution
+   * goto-symex
+
+
+- solvers
+  * solvers
+
 \section other-apps Other apps
 Other Useful Code
 -----------------