Configure asterisk alignment in multiline comments to match scaladoc recommendation

[mjp4]

Adds an option g:scala_scaladoc_indent = 1 to enable comments using the official Scaladoc style.

/**
  * Scaladoc comment with g:scala_scaladoc_indent = 1
  */

/**
 * Doc comment with g:scala_scaladoc_indent = 0 or not set.  This is the current behaviour
 */

Referenced in https://github.com/derekwyatt/vim-scala/issues/116

[ches]

Does this behave okay if you start the comment on the first line, the /** one? That's pretty common in projects that use this style. If formatting comments with gq behaves poorly in that case it may be hard to work around Vim's behavior for that, not sure.

Finally, please add the info to the vimdoc in doc/scala.txt, that's more import than the README IMO.

[mjp4]

It behaves fine with the comment on the first line. I have made all the improvements you suggested and tested them. I have combined all the changes into a single commit.

[ches]

Thanks @mjp4, sorry about the delay in reviewing!

[mjp4]

Thanks :-)