Isolate Application object in Env:

This change causes each instance of Env to construct its own
isolated Application object for testing. Also included is
part of a framework to create multiple Application objects
in the same unit test and connect them together.

src/ripple/basics/BasicConfig.h

@@ -175,6 +175,9 @@ public:
         If the section does not exist, an empty section is returned.
     */
     /** @{ */
+    Section&
+    section (std::string const& name);
+
     Section const&
     section (std::string const& name) const;
 
@@ -183,6 +186,12 @@ public:
     {
         return section(name);
     }
+
+    Section&
+    operator[] (std::string const& name)
+    {
+        return section(name);
+    }
     /** @} */
 
     /** Overwrite a key/value pair with a command line argument

src/ripple/basics/impl/BasicConfig.cpp

@@ -96,6 +96,12 @@ BasicConfig::exists (std::string const& name) const
     return map_.find(name) != map_.end();
 }
 
+Section&
+BasicConfig::section (std::string const& name)
+{
+    return map_[name];
+}
+
 Section const&
 BasicConfig::section (std::string const& name) const
 {