hdf5_der

Cache image removal tool
1) Modify the tool "h5clear" to add "removal of cache image" functionality
2) Modify/add tests for "h5clear"
3) Add public API H5Fget_mdc_image_info() to get info about cache image in the file
Tested on moohan, mayll, platypus, ostrich, osx1010test, quail, kite, kituo.