Performance

- Added Timer class to display high resolution timing information.
- Found terrible bug in Table::optimize that was taking up 99.7%,
  on average, of the Table::rendering time, including sorting.  This
  fix naturally causes a 187-fold speedup of rendering.
- Changed report.cpp in handleCustomReport to only load pending tasks,
  instead of all pending tasks.  Subtle, but important difference.

src/Makefile.am

@@ -1,2 +1,2 @@
 bin_PROGRAMS = task
-task_SOURCES = Config.cpp Date.cpp T.cpp TDB.cpp Table.cpp Grid.cpp color.cpp parse.cpp task.cpp command.cpp report.cpp util.cpp text.cpp rules.cpp Config.h Date.h T.h TDB.h Table.h Grid.h color.h task.h
+task_SOURCES = Config.cpp Date.cpp T.cpp TDB.cpp Table.cpp Grid.cpp Timer.cpp color.cpp parse.cpp task.cpp command.cpp report.cpp util.cpp text.cpp rules.cpp Config.h Date.h T.h TDB.h Table.h Grid.h Timer.h color.h task.h