Integration - "projects" report

- "projects" report converted to 1.8.0.
- Relocated code from task.cpp to recur.cpp to allow unit tests to link
  without includign task.cpp and therefore main.
- Removed obsolete sandbox directory.
- Fixed bug where Config::load deleted the pre-loaded custom reports.
- Fixed bug where Cmd::valid failed to include custom reports properly.

src/Config.cpp

@@ -85,8 +85,6 @@ Config::Config (const std::string& file)
 // not tolerated, but blank lines and comments starting with # are allowed.
 bool Config::load (const std::string& file)
 {
-  this->clear ();
-
   std::ifstream in;
   in.open (file.c_str (), std::ifstream::in);
   if (in.good ())