Skip compute of altered results and disable the play button in editors

The TXMResult.compute method erases modifications and the result is not protected from hierarchy re-computing (ex: CA can re-compute the LT, Concordances can re-compute their lines) -> TXMResult.compute should skip the compute if the result is altered (modifications will not be lost).

The alert dialog of the play button is not enough to protect the user from errors -> the button should be disable if the result is altered.

Checking procedures

1. modify a LT, check if Compute button re-builds the LT and call an CA on the LT and verify that the LT is not re-computed
2. modify a Concordance and check if Compute button re-builds the concordance lines