Improve formatting of help on algorithms in python

[Nick Draper]

LoadSNSEventNexus(Filename, OutputWorkspace, FilterByTofMin=None, FilterByTofMax=None, FilterByTimeStart=None, FilterByTimeStop=None, BankName=None, SingleBankPixelsOnly=None, LoadMonitors=None, Precount=None, execute=True)
    Loads a SNS EventNeXus format file.
    Optionally, you can filter out events falling outside a
    range of times-of-flight and/or a time interval.
    
      Filename(Input:req) *string* 
          The name (including its full or relative path) of the Nexus file to
    attempt to load. The file extension must either be .nxs or .NXS [.nxs]  OutputWorkspace(Output:req) *class boost::shared_ptr<class Mantid::API::IEventWorkspace>* 
          The name of the output EventWorkspace in which to load the EventNexus file.  FilterByTofMin(Input) *number* 
          Optional: To exclude events that do not fall within a range of times-of-flight.
    This is the minimum accepted value in microseconds.  FilterByTofMax(Input) *number* 
          Optional: To exclude events that do not fall within a range of times-of-flight.
    This is the maximum accepted value in microseconds.  FilterByTimeStart(Input) *number* 
          Optional: To only include events after the provided start time, in seconds (relative to the start of the run).  FilterByTimeStop(Input) *number* 
          Optional: To only include events before the provided stop time, in seconds (relative to the start of the run).  BankName(Input) *string* 
          Optional: To only include events from one bank. Any bank whose name does not match the given string will have no events.  SingleBankPixelsOnly(Input) *boolean* 
          Optional: Only applies if you specified a single bank to load with BankName.
    Only pixels in the specified bank will be created if true; all of the instrument's pixels will be created otherwise.  LoadMonitors(Input) *boolean* 
          Load the monitors from the file (optional, default False).  Precount(Input) *boolean* 
          Pre-count the number of events in each pixel before allocating memory (optional, default False). 
    This can significantly reduce memory use and memory fragmentation; it may also speed up loading.

[Martyn Gigg]

(In [9538]) Fix problem with saving certain paths after the default save directory had been appended to it. Fixes #2445 Also improve python simple algorithm functions help documentation with a few new lines to make them clearer. Fixes #2459

[Owen Arnold]

Verified.

[Stuart Campbell]

This ticket has been transferred to github issue ​3307