Unification of workflow descriptions & KNIX specific extensions to ASL description about knix

[iakkus]

Started implementation on branch feature/asl_knix_flags.

[iakkus]

Added some test cases that utilize session functions as well as checkpoints flag. These tests pass.

Need to update GUI for validation checks.

[iakkus]

The complete list of KNIX-specific flags:

1. SessionFunction (bool): specifies whether this function is a session function (default: false)
2. SessionFunctionParameters (dict): specifies the parameters of a session function (default: {})
3. EnableCheckpoints (bool): specifies whether checkpoints between states should be taken (default: true)
4. AllowImmediateMessages (bool): specifies whether functions can send immediate messages to other functions to trigger them asynchronously (i.e., no response). The usage of sendToFunctionNow() API call can cause unexpected behavior, because the triggered function can continue making transitions in the specified state machine. (default: false)
5. WaitForNumBranches (list (int)): specifies how many branches of a Parallel state need to be finished before transitioning to the next state. There can be multiple such values and hence, multiple transitions. The usage of WaitForNumBranches can cause unexpected behavior, because the triggered function may continue making transitions in the specified state machine. (default: [num_total_branches_in_parallel])

[iakkus]

In the API docs, we should add warnings to the API functions that are relevant to KNIX-specific features. These include:

1. session related functions
2. immediate message functions
3. dynamic workflow manipulation functions
4. CRDT operations
5. any others?

Edit: Issues #45 and #46 are about API docs. These could be added there.