build+docs: Add doxygen generation target

This commit also fixes few documentation errors

Change-Id: Ie34eaf167b7e423c82c1e453fbd0bbf2ac2c805c
diff --git a/src/group-manager.hpp b/src/group-manager.hpp
index f2d439d..e4674df 100644
--- a/src/group-manager.hpp
+++ b/src/group-manager.hpp
@@ -47,7 +47,7 @@
   /**
    * @brief Create group manager
    *
-   * The namespace of group manager is /<prefix>/read/<dataType>/
+   * The namespace of group manager is /[prefix]/read/[dataType]/
    * The group management information (including user cert, schedule) is stored in a database
    * at @p dbPath.
    * The group key will be an RSA key with @p paramLength bits.