Issue #81: diff view: copy code improvements (conservancy/kallithea)

[Thomas De Schampheleire]

New issue 81: diff view: copy code improvements
https://bitbucket.org/conservancy/kallithea/issue/81/diff-view-copy-code-improvements

Thomas De Schampheleire:

Copying code from a diff view is somewhat odd:
- when selecting lines, the line numbers are part of the selection
- when pasting, the line numbers are not present (which is a good thing in fact)
- but blank lines are introduced in between each line

It would be nicer if:
- during selection, only the code is selected
- pasting does not insert blank lines