This PR enable scalafmt-cli to automatically fetch a scalafmt of which
version matches the `version` setting in `.scalafmt.conf`.
This change will help syncing the version of scalafmt among
build tool integrations, editor integration, and scalafmt-cli.

See: scalameta#1318
     scalameta#1346

…claration

1) Moved everything related to downloading process to
ScalafmtDynamicDownloader
2) Created errors ADT for all currently reported error types
3) Split format method to two: one returns machine readable error from
from errors ADT hierarchy, another one handles the error and reports
user-readable message to provided reporter

1) move invoke and invokeAs to implicit ops class methods
2) add invokeStatic implicit method for classes
3) rearrange classes and methods loaded from classLoader
4) unified field names for loaded classes

- resolve error during download
- unknown exception during download: network errors, possible NPE etc...
- corrupted classpath exception: for cases when reflection operations
inside ScalafmtReflect cause unhandled exceptions

- ScalafmtDynamic is now responsible for both config caching and
scalafmt caching
- ScalafmtDynamic is now responsible for checking for checking whether
source file matches config includes/excludes filter
- ScalafmtReflect now simply represents a wrapper around Scalafmt
instance of a specific version, providing us an interface that
encapsulates all reflection stuff

…eference

- Load a scalafmt jar using scalafmt-dynamic only when
  scalafmt-cli's version doesn't match specified `version` setting.
  If the version matches, scalafmt-cli formats codes using
  pre-resolved scalafmt to save the overhead for resolving scalafmt
  jar on runnning.
- Create tempFile that contains configration string specified by
  `--config-str` option for passing configration to scalafmt-dynamic.

…lameta#1282

- Test for the behavior if .scalafmt.conf is missing.
- Test for the behavior if `version` setting is missing.

Indent Operator Fix

Make scalafmt-cli to use scalafmt-dynamic module instead of depending on specific version of scalafmt-core.

… stdlib

…ala v2.11.x

…integrate-with-intellij

1344 api changes to integrate with intellij

…fmt-org

Update website for sbt-scalafmt 2.0.0-RC5

```scala
// Before
for (a <- as)
yield
  Future {
    // ...
  }
// After
for (a <- as)
yield Future {
  // ...
}
```

It's possible to get the old behavior with `newlines.avoidAfterYield = false`.

While working on this change, I observed that
`style.indentYieldKeyword=true` (default) has undesirable (and
unexpected) behavior for val definitions.
```scala
// Before
val x = for (a <- as)
  yield a
// After
val x =
  for (a <- as)
    yield a
```
The new behavior is more consistent with how we handle other val
definition bodies. By forcing a line break before `for`, we make
it easier to associate the `for` keyword with its accompanying `yield`.

hehe seems the scalafmt repo uses and old scalafmt version that doesn't
automatically remove trailing commas. Will upgrade in separate PR.

Avoid newlines after yield keyword.

There are a few regressions in the output IMO but I can live with them.

Update changelog and document release process

Upgrade to latest scalafmt.

Upgrade IntelliJ plugin