fix parsing error : return commands even when the end of the file contains parsing error

[Alidra]

When working with Vscode or Emacs, if a Lambdapi file contains parsing errors, the parsing phase should return the commands that have been successfully parsed (this is already the case with the command line Lambdapi).

This PR fixes this issue.

Additionally, this PR changes the way navigating the proofs is done in Vscode with the navigate until cursor.
Instead of stopping the green zone at the beginning of current the line, the green zone is expended to the end of the current command.

Finally, this PR fixes stops the green zone before the { delimiter (and incidentally begin delimiter) to avoid that the LSP server answers with subgoals of the next tactic missing the current one as described in issue #1049

[Alidra]

@fblanqui , Can you check if the behavior described in this PR suites you?

[Alidra]

@fblanqui, as discussed earlier today, the modifications in this PR work fine with both Vscode and Emacs.
We still need to fix the syntax error message in Emacs terminal but it is better to do it in a separate PR.

Thus, I believe the PR can be merged.

[fblanqui]

Thanks Abdelghani!