Propose all possible extractions in ExtractCode

This PR changes ExtractCode such that it does no longer filter the available extractions based on the side effect detection heuristic. This results in more proposed extractions but is more flexible.

After applying this PR, the "Extract..." command in Scala IDE can replace the remaining extraction commands "Extract Value", "Extract Method", "Extract Parameter" and "Extract Extractor".
Merge pull request #54 from Luegg/fixExtractCode

Propose all possible extractions in ExtractCode