Write new formatting engine

PSSA2 currently only has an analyzer. It should also have a formatter.

In particular, the API should allow objects to implement an abstract class that doesn't emit diagnostics, but instead contributes edits to a formatting buffer.

Rules should be able to provide an implementation for this also by implementing an API that provides an instance of the required abstract class.

Requirements are:

• Run as many formatters over the script as it can at once
• When formatters want to overwrite the same extent, the largest wins
• Attempt to run until no more formatters have edits to make, up to some maximum number of runs
• Formatters should reuse the rule configuration system

まず既存のアナライザーとルール設定システムを読み、次に formatter API がそれらと並んでどのように適合できるかを把握します。完了条件は、formatter インスタンス、最大の重複を優先する動作を伴う同時編集、上限までの繰り返し実行、再利用されるルール設定をサポートすることです。