FAQ entries #dumpload and (new) #fix-nonLF-log

I have extended the FAQ entry #dumpload [1], about the dump+load
procedure, with some caveats and details on the technique to dump+load
a large repository with minimal downtime. This is based on a users@
mail from last year [2] (I had been meaning to convert this into a FAQ
since then, but only now got around to it). See my edits in r1803274
and r1803323. Questions on how to correctly execute a dump+load
(possibly from a very old repository) still come up regularly on
users@.

I have also written a new (related) entry #fix-nonLF-log [3],
describing how to fix the "svnadmin: E125005: Cannot accept non-LF
line endings in 'svn:log' property" error one might run into during
'svnadmin load'. See r1803336.

These FAQs more or less cover one of the whiteboard items from the
2015 hackathon [4] (namely "document ideal procedure for full
dump/load with minimal down-time").

Review, additions, rewriting, ... welcome :-).

Also: this reminds me of those other whiteboard items from 2015:
"svnadmin load --normalize-revprops", "- normalize svn:* props", "-
normalize mergeinfo", to get 'svnadmin load' on par with svnsync
regarding normalization. Having those options (at least the first two)
would make those faq answers a lot shorter ... If anyone has some
cycles to spare, 1.10 might be a good target to try and get these in
...

[1] http://subversion.apache.org/faq.html#dumpload

[2] https://svn.haxx.se/users/archive-2016-06/0098.shtml

[3] http://subversion.apache.org/faq.html#fix-nonLF-log

[4] https://svn.haxx.se/dev/archive-2015-09/0187.shtml

-- 
Johan