Adding selection for ParagraphPrevious and ParagraphNext.

[hchac]

Also tweaked the behavior of Paragraph/{Previous/Next} so that it skips all empty lines immediately next to cursor position, until it finds the start/end of the paragraph closest to it. Once it finds the paragraph closest to it, the same behavior as before applies. With the previous behavior if the cursor was surrounded by empty lines, then Paragraph/{Previous/Next} would only jump to the next empty line, instead of jumping to the start/end of a paragraph.