expectation files and blocks of tests

There is an in-practice structure in the expectation files where some tests are added in a block. Those blocks start with a comment and end with an empty line.

• When uprev updates expectations, the previous block may not be closed with an empty line, as it is the end of the file. Then the tool must add this empty line to separate the new changes to the block.
• Also, it will be helpful, when the expectations clean a block (we only have the comment and the empty line), to clean also comment as it doesn't have sense anymore.
• The test strings in the block must be alphabetically sorted.