magit-edit-log.el: define keymap before mode

Otherwise the variable would already be bound once the
defvar is evaluated causing it not to do anything.
merge toplevel sections "Acting (1)" and "Acting (2)"

Until recently the toplevel section "Log Edit Mode" was between these
two sections, but that was moved to a separate file.

To merge these two sections another toplevel that was between the two
had to be made a subsection.  In the process that section "ChangeLog"
was renamed to "Commit".  In the future it will also contain a command
`magit-commit', which will be a wrapper around `magit-log-edit' or the
respective function from `git-commit-mode'.
allow using magit-add-log during rebase

Like `magit-log-edit' this function detected an progress rebase and
offered to continue that instead of committing.  When the user reply
was "no" this function acted as if that means "no I want to do
anything at all".  `magit-log-edit' already understands it correctly
"no thanks, I really do want to commit".

Change this function to behave the same way.  Because this function
used `magit-log-edit' internally the test for an in-progress rebase
can be removed here.  There is some code before the call to
`magit-log-edit' but that only collects some information, has no side
effects, and is inexpensive.
refactor log commands

Prompt the user for the range in the `interactive' forms of
`magit-log-ranged' or `magit-log-long-ranged'.

Previously this was not only done outside of the `interactive' form
of these functions but inside of `magit-log'/`magit-log-long' which
are called by the former.

This is wrong for two reasons:

(1) Whenever possible minibuffer input should be read in the
    interactive form.

(2) `magit-log'/`magit-long-log' only ever used the range when
    called by `magit-log-ranged'/`magit-log-long-ranged'.

`magit-log'/`magit-log-long' now take a RANGE as first argument,
replacing the "ask the user for a range and use that" switch
previously used.

Since this change affects almost all lines seize the opportunity
and move the "Logging" section into the toplevel "Acting" section.
name the reflog commands correctly

Rename `magit-reflog' to 'magit-reflog-head' and
rename `magit-reflog-ranged' to `magit-reflog'
reverting 8fcae59c9f15c3519fc9145b7b331ee8c2df80bf.

Also read the rev in the interactive form of `magit-reflog'.
For rational see 13d21ce5ac431ca906e2d1862d6e01e488bfd8da.