log: Add whitespace ignore options

log: Add whitespace ignore options

Similar to what we did with diff, implement whitespace ignore options
for log too.  This requires us to define some means of creating any
RawText object type at will inside of DiffFormatter, so we define a
new factory interface to construct RawText instances on demand.

Unfortunately we have to copy the entire block of common options.
args4j only processes the options/arguments on the one command class
and Java doesn't support multiple inheritance.

Change-Id: Ia16cd3a11b850fffae9fbe7b721d7e43f1d0e8a5
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>