Format doc (from devtools to energy_functions)

Devtools, distributions and energy_functions
Format documention in expr/basic

Includes important changes to the docstring of symGivens2
Format documentation in expr
Format doc in gui (and format)

The change in format is very minor.
Format documentation in linear
Display multiple levels of indentation correctly
fixes the issue #490 such that SparseDataset works with the new style of the iterator with data_specs
Remove tabs
adding a test unit for issue #490 in addition to completing the SparseDataset class
removing a comment
correcting comment #490
updating issue #490
updating the issue #490 to add module_level docstring
updating ticket #490 to cover the comments of Xavier.
updating issue #490 to apply comments of Xavier
applying modification for ticket #490 to use Train object.
changing a comment for issues #490
adding comments to the dummy classes in test_sparse_dataset (ticket #490)
Updating the test_sparse_dataset for ticket #490 to update module_level and
class level comments
updating the DummyCost Class for ticket  #490