New step remove sftp file

[gbarat87]

This step is to remove a file from the sftp server.
This is needed as there is no possibility to move a file from a folder to another in the sftp server.
The step "sftp copy file" following by this new one can allows one to move a file around.

[matthewhilton]

Could this also have unit tests added? e.g. see https://github.com/catalyst/moodle-tool_dataflows/blob/MOODLE_405_STABLE/tests/tool_dataflows_sftp_test.php
Since there's no actual SFTP to test against, it might just end up being a test for 1. sanity check that step loads properly, and 2. testing that source is always a remote, and errors otherwise

[matthewhilton]

Another thought - could this also be added as a flow step just for consistency - you should be able to share most of the functionality with the trait

[gbarat87]

@matthewhilton Thank you for the review.
After testing, I ave decided to simply add the step "rename" to allow to rename a file in the sftp server. That is making the move easier.
I decided to keep the delete step as it can be useful as well.
All the methods have been moved to a trait to reuse the same code.

[matthewhilton]

Gave this a test locally and works as expected, including field validation (for reference, I used https://hub.docker.com/r/atmoz/sftp)

Just 1 tiny change regarding some lang strings.

Also because we changing the lang strings the version.php needs a bump

[matthewhilton]

Thanks for updating those lang strings @gbarat87 - the CI is failing now because of the php copy paste detector. Honestly i'd be open to disabling it to get the ci green as it isn't super valuable.