#779 Java formatter: no longer format single line comments.

• Best to review per commit.
• Changes:
  • Java formatter: no longer format single line comments.
  • Checkstyle: check for space after start of single line comment. Some exceptions:
    • Allow // at the end of a line.
    • Allow ///-like headers.
    • Only check if space before comment, to allow URLs (https://..., tooldef://...) etc.
  • Fix few single-line comments that violate the new Checkstyle rule.

Closes #779 (closed)