merge two subsections of toplevel "Magit Mode"

In preparation of future changes merge two subsections of toplevel
section "Magit Mode".  Keep the heading "Display Buffer" and dispose
of "Find Buffer".  The functions previously located below the latter
heading (`magit-find-{,status}-buffer') are not actually used by the
functions now located in the same section.  The "find" functions will
later be replaced by other functions, which will then be used by the
others.  Never-the-less the definitions the latter functions are the
ones that were moved because the new location makes more sense and
also allows splitting of another subsection into a new toplevel
section (see next commit).
move definition of magit-map-magit-buffers

Move the definition of function `magit-map-magit-buffers' into a new
subsection of "Magit Mode", named "Mode Utilities".  That isn't optimal
because its the only function in that new section, but that might change
over time.  Randomly sticking it into one of the section that happens to
contain a function that uses it, is what we did before.
move  magit-{revert-buffer,update-vc-modeline} into "Refresh Machinary"

Move the definitions of the functions `magit-revert-buffer' and
`magit-update-vc-modeline into the "Refresh Machinery" section.

Previously they were located in the "Refresh Buffer" section which also
contains (now only) `magit-refresh-buffer'.  All of these functions are
used to "do a refresh", the latter for Magit buffers and the moved
functions for file-visiting buffers.  I am consolidating the various
"Magit Mode" subsections and turning "Refresh Machinery" into a toplevel
section (see later commits).  While the new (just like the old) location
isn't perfect, it is an improvement, given the above objectives.
move "Refresh Machinery" section to toplevel

Move the "Refresh Machinery" section to the toplevel.  Previously it
was a subsection of "Magit Mode".  The main reason it was merely a
subsection for a long time, is that moving it to the toplevel did
require some code to be moved around (see previous commits).

The refresh machinery is only loosely coupled with the code related
to the code in "Magit Mode".  This move just officializes this, and
was prone to happen eventually.  Since I have plans to improve both
the "mode" and the "refresh" logic, that moment has come now.
move definitions of magit-refresh-{function,args}

Move the definitions of the variables `magit-refresh-functions' and
`magit-refresh-args' to another subsection of "Magit Mode".  Previously
they were located inside the subsection "Hook" which somewhat made sense
because they are used in a hook-like fashion.

However the other functions in that section of "Magit Mode" are hook
functions that are necessary because of limitations in the section
code (or used by them).  This limitations will eventually be lifted
making these kludges unnecessary.

The current heading of the new section, "Initialize Mode", doesn't do
the moved functions full justice and is subject to change.
rename "Hooks" subsection to "(section kludges)"

The functions in the "Hooks" subsection of "Magit Mode" are hook
functions that are necessary because of limitations in the section
code (or used by them).  This limitations will eventually be lifted
making these kludges unnecessary.

Until then at least label them accordingly.
move subsection "(section kludges)" to end of "Magit Mode"

The functions in the "(section kludges)" subsection of "Magit Mode" are
hook functions that are necessary because of limitations in the section
code (or used by them).  This limitations will eventually be lifted
making these kludges unnecessary.

Until then at least move them out of sight.
merge three subsections of "Magit Mode"

Merge the subsections "Initialize Mode", "Display Buffer", and "Refresh
Buffer" into a new subsection "Mode Foundation".  The old distinctions
did make sense, but after past cleanup it is no longer *necessary* to
keep them separated to improve the odds of understanding them.  The
functions and variables are closely related, and interconnected, so
having them in the same section makes sense.
magit-refresh-{function,args}: no longer permanently local

No longer define variables `magit-refresh-function', and
`magit-refresh-args' as permanently buffer-local.  They are still
buffer-local.  Making them permanent local doesn't make any sense:

* we don't actually change the mode in buffers where these are set,
* if we did change the mode we would *not* want them to keep their
  old values, and
* they would not do so anyway, because we explicitly reset them.
rename function magit-{ => mode}-refresh-buffer

Rename the function `magit-refresh-buffer' to `magit-mode-refresh-buffer'
making it more obvious that this is only useful for buffers whose major
modes are derived from Magit mode.
magit-mode-display-buffer: fix typo in doc-string
rename function magit-{ => mode}-quit-window

Rename the function `magit-quit-window' to `magit-mode-quit-window'
making it more obvious that this is only useful for windows whose
current buffer's major modes are derived from Magit mode.
rename magit-display-mode-buffer to magit-mode-display-buffer

Rename function `magit-display-mode-buffer' to
`magit-mode-display-buffer', for consistency
with other similarly named functions.
remove function magit-find-status-buffer

Remove function `magit-find-status-buffer' and just use generic
`magit-find-buffer'.  The latter will be renamed and extended in
subsequent commits and then more often used for other modes too;
it which point it won't makes sense anymore, to have a specialized
function for just one of the modes (and adding one for all modes
certainly isn't an option).
move magit-mode-quit-window to end of its section

Move the function `magit-mode-quit-window' from the middle to the end of
section "Mode Foundation".  It is closely related to the other functions
in this section but is different in that does not "create" a mode buffer
but makes it go away.  The end seems like a suitable place for that.
Merge branch 'pr/consistent-Magit-Mode'