Now prints JSON versions of feeds when given --json.

Also handles flags correctly by using @local_argv inside main() rather
than the unmodified @ARGV - a bug lingering from copypasta of wrt-display
code.

This stashes the HTML version of every entry in memory and uses
Mojo::DOM to extract headers from the markup for use as titles.
Titles are displayed in $self->{page_navigation}, now available
inside templates as ${page_navigation}.

In order to keep Mojo::DOM from choking on other input, it uses the open
pragma to open everything as UTF-8 by default, which also eliminates a
whole class of character encoding bugs and removes some fiddling with
Encode::decode() from feed_print().

This is all obviously a more memory-intensive, but caching the markup
turns out to have the side effect of making it much faster to render
even a large site, probably as much as anything because the HTML in
question is only getting generated once per entry instead of
(potentially) 2-3 times.

This commit isn't very atomic.  In the process of roughing it out and
testing it, I made a small pile of minor but potentially breaking
changes:

  - Removed entry_map from settings and hardcoded handling of various
    types of entry as some if-statements instead.

  - Removed embedded_perl flag in settings - was always turned on in
    practice, and wasn't very coherent since templating would have
    broken without it.

  - bin/wrt-display - now handles the "feed" alias correctly

  - EntryStore: now supports retrieving values for properties with
    prop_value() - this isn't currently used, but it seems like a
    reasonable extension of the property idea.

  - Added `wrt ls --with-titles`.

  - Added dependency versions to Build.PL.

  - Refactored Markup's line_parse() a little.

  - Refactored some tests to give cleaner / more useful output.

  - Renamed default template file to "default".

These display helptext and current version of the application,
respectively.

`wrt -h` and `wrt --help` still work, as do a new `wrt --version` and
`wrt -v`.  I think the subcommand forms are useful (and echo a growing
norm for this kind of interface), but the others should be discoverable
for users with traditional expectations.  Both basic help and version
info should be readily available without much thought, which I think
justifies the repetition.

wrt-ls is a provisional interface to the tools in WRT::EntryStore.  It
should do more, but work is needed that I'm not going to put in before
releasing v5.0.0.

This seems like a good point to call things stable for this major release.
I have a bunch of ideas that I'd like to implement for a v6, which might
well break the API and underlying data structures.

This is all pretty academic since no one else actually uses this thing.

Adds a wrt-init kind of on the model of git init for starting a stub
directory with wrt.json, archives/, publish/, and templates/.

Also starts to tweak POD a bit.

These used to live in bpb-kit; moving them in here since they're specific
to the wrt format.

Now uses:

  wrt display
  wrt render-all
  wrt fcgi

It's shorter and the letters are all right there on the keyboard.

Rolls in render.pl stuff from p1k3.  Now gets deployed system-wide,
to /usr/local/bin.