API for improved Unit Testing (RIPD-432):

* Added new test APIs allowing easy ways to create ledgers, apply
  transactions to them, close and advance them.

* Moved Ledger tests from Ledger.cpp to Ledger.test.cpp.

* Changed several TransactionEngine log priorities from lsINFO to lsDEBUG to
  reduce unnecessary verbosity in the log messages while running these tests.

* Moved LedgerConsensus:applyTransactions from a private member function to a
  free function so that it could be accessed externally, and without having to
  reference a LedgerConsensus object.  This was done to facilitate the new
  testing API.

Builds/VisualStudio2013/RippleD.vcxproj

@@ -1730,6 +1730,9 @@
     </ClCompile>
     <ClInclude Include="..\..\src\ripple\app\ledger\Ledger.h">
     </ClInclude>
+    <ClCompile Include="..\..\src\ripple\app\ledger\Ledger.test.cpp">
+      <ExcludedFromBuild>True</ExcludedFromBuild>
+    </ClCompile>
     <ClCompile Include="..\..\src\ripple\app\ledger\LedgerCleaner.cpp">
       <ExcludedFromBuild>True</ExcludedFromBuild>
     </ClCompile>

Builds/VisualStudio2013/RippleD.vcxproj.filters

@@ -2586,6 +2586,9 @@
     <ClInclude Include="..\..\src\ripple\app\ledger\Ledger.h">
       <Filter>ripple\app\ledger</Filter>
     </ClInclude>
+    <ClCompile Include="..\..\src\ripple\app\ledger\Ledger.test.cpp">
+      <Filter>ripple\app\ledger</Filter>
+    </ClCompile>
     <ClCompile Include="..\..\src\ripple\app\ledger\LedgerCleaner.cpp">
       <Filter>ripple\app\ledger</Filter>
     </ClCompile>