Refactor to support ChangeCorrectionProposal

[Eskibear]

Fix #1103

Motivation

CUCorrectionProposal is dedicated for TextChange. This PR a prerequisite for composite changes like "create new type", which involves:

• ResouceChange to create a file
• TextChange to insert the content
• A custom command (optional, if you want to tell client to switch focus onto the newly created file)

Changes

• commit c21ec02
  • Change the copied proposals to extend ChangeCorrectionProposalCore and CUCorrectionProposalCore from jdt directly, and remove unnecessary classes.
  • Change Collection<CUCorrectionProposal> to Collection<ChangeCorrectionProposal> if necessary.
• commit 3540f82 is trivial as the commit msg says.

[Eskibear]

CI failed on the same case as #1095 (comment) , re-open to retrigger.

[fbricon]

instead of closing/reopening the PR, you can add a comment test this please, that will trigger a new jenkins build

[fbricon]

test this please