Add supertask runtime estimation

[zyronix]

Continued the work of @SherlockNL on the supertask runtime estimation pull request. See for more information #696

Show estimated total runtime of a supertask, allowing the user to interactively come to the desired size of a supertask by adding or removing subtasks on the supertask detail page

Features:

• Allow adding and removing subtasks to supertask
  

• Save line count of dictionary files and rule files in database
  

• Parse hashcat commands to compute keyspace size. Gratefully uses the code submitted by shivanraptor in #672 
  

• Thank you, shivanraptor, for sharing your code with the community!
  

• Compute runtime per pretask of supertask, depending on benchmark values entered by the user
  

• Currently supports -a0 and -a3 hashcat attacks. Adds 'Unknown' to total runtime estimate when not every subtask runtime could be estimated
  

• Supports custom charsets for masks in -a3 attacks
  

Future work and additional remarks:

• To do: add support for other hashcat attack modes
  

• To do: make the hashcat command parser more robust towards syntax differences in hashcat commands. Note however, that some of these are already taken into account in this commit, such as the difference between "-a0" and "-a 0" for example, or when the command includes consecutive spaces
  

• Note: the runtime estimate entirely depends on parsing hashcat commands. A pretask meant to be run by another cracker will result in an unknown runtime estimate.
  

Implemented feedback of @s3inlc and merged master into the pull request.