Changed indentation rules to only apply when enter is pressed, to fix…

[onelivesleft]

… copy+paste & move line being broken.

Fixes #127

[onelivesleft]

Fixes #69

[onelivesleft]

N.B. I looked at how the python extension does it, since it's a language people have been working with for a long time. They use OnEnterRules exclusively, and do not mess with auto-indent/dedent, which makes sense for a language with (A) semantic indentation and (B) no end-of-block delimiter.

Note this comment:

            // Note that we do not currently have an auto-dedent
            // solution for "elif", "else", "except", and "finally".
            // We had one but had to remove it (see issue #6886).

Issue#6886 is their version of the issues listed in this PR: microsoft/vscode-python#6886