text: Title: [FEA] hypergraph  Directly Follows edges for process mining
  Body: **Is your feature request related to a problem? Please describe.**
  
  We should be able to create Event Graphs for process mining: https://towardsdatascience.com/introduction-to-process-mining-5f4ce985b7e5
  
  The main missing piece seems to be a flag for `Directly Follows`
  
  
  **Describe the solution you'd like**
  
  ```python
  hypergraph(df, cols, directly_follows=True, direct=False) # links successive event nodes
  hypergraph(df, cols, directly_follows=True, direct=True) # links entities of successive event nodes
  ```
  
  * [ ] Default off hypergraph param `directly_follows`
  * [ ] When `direct=False`: creates new event=>event edges of type `directly_follows`
  * [ ] When `direct=True`: creates new entity=>entity edges of type `directly_follows`
  * [ ] int64 column `directly_follows_step`
  * [ ] Should work for all engines
  * [ ] Tested
  * [ ] Documented
  * [ ] Tutorial
  
  **Describe alternatives you've considered**
  
  * We should check libraries for additional common shapes
  
  * Additional options:
  
  ```python
  directly_follows_step_offset=0 # initial number to count from
  directly_follows_attributed=True # control whether to add some/all attrs
  directly_follows_ordering_dimension='some_col' # default to current order
  directly_follows_max_threshold='30s' # only link if next even in a threshold, default=None
  directly_follows_predicate=lambda (prev, next): True # only link when True
  ```
  
  