logcat: Adjust help to make it more meaningful

It is not clear about the long option aliases, list
them comma separate first for clarity. Squash lines
of help content if possible. Lock to 3 indents, one
for options, another for text on same line as options
and another for next line or continuation.

Bug: 28120456
Change-Id: I5331acde3ac0fd3b87f6699ba108f6cef46a1563