Xapian supports an "ngrams" option to help with languages/scripts
without explicit wordbreaks, such as Chinese / Japanese / Korean.
Add some plumbing for supporting this in mu as well. Experimental for
now.
It can be faster to feed big mu -> mu4e data, such as contacts are
message headers through a temp-file instead directly though stdout;
implement this, and add the server parameter --allow-temp-file.
Implement this the "contacts" and "find" commands.
For expanding shell options (with expand_path / wordexp)
Note that e.g. in zsh: --maildir=~/Maildir is handled (program receives
--maildir=/home/user/Maildir) but e.g. bash does not do that, and the
program receives the literal '~/Maildir'
We expanded this in mu earlier, so let's do that again.
Implement a new command-line parser, based on CLI11.
It's a bit more C++'ish, and allows for a lot of fancy things... some of
which we have implemented here.
Update the various commands to use the new Options struct
Remove the old help strings; instead e.g. `mu help view` opens the
manpage.
Integrate the guile scripts more tightly.
