Replace "Usage Rules" by "Trigger Conditions"

[bqth29]

Please check if the PR fulfills these requirements

• [x] The commit message follows our guidelines
• [x] Tests for the changes have been added (for bug fixes / features)
• [x] Docs have been added / updated (for bug fixes / features)

Does this PR already have an issue describing the problem? Fixes #992

What kind of change does this PR introduce? Usage Rules have been discarded and replaced by Trigger Conditions that carry a sort of logical gates on four conditions: instant, contingency, cnec and country.

Does this PR introduce a breaking change or deprecate an API?

• [x] Yes
• [ ] No

If yes, please check if the following requirements are fulfilled

• [x] The Breaking Change or Deprecated label has been added
• [ ] The migration steps are described in the following section

What changes might users need to make in their application due to this PR? (migration steps)

TODO

Other information:

[bqth29]

Since the code must be made common with PowSyBl (cf. #1067) I suggest to close this PR for the moment