gitk: Make more options easily accessible from Edit View dialog

gitk: Make more options easily accessible from Edit View dialog

Commit 218a900bd8efd0d49f8a0d9491aa4786a998d4f4 added a number of new
individual fields for the Edit View dialog to make them more accessible
to end users, while still allowing all options to be specified in the
"arguments to git log" field.  This extends the dialog further, to
include refs, author, committer, commit message, and patch contents.
As before everything still remains accessible from the "arguments to
git log" input field.

Additionally, this provides hints for the format of the various input
fields (for example, listing some sample date strings in different
formats), and puts related query items into subsections to make it
easier to digest the number of options that exist.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>