Fix duplicate shortcut usage in sign/verify message dialog.
update 2 command-line parameter help messages

- -checkpoints is now much more understandable and should be way easier
  to translate
- -loadblock uses the same format (blk000??.dat) as -reindex
Remove 'T' from debug log timestamps

Space separation between major fields is easier for human eyes and
libs to parse.
Merge pull request #2133 from Diapolo/init_strings

update 2 command-line parameter help messages
Merge pull request #2032 from burger2/fix_shortcut

Fix duplicate shortcut usage in sign/verify message dialog.
Remove 'T' from remaining date/time format strings.
test/util_tests.cpp: one more DateTimeStrFormat 'T' removal