chore(package.json): add scripts to automate starting, stopping and updating

The default method to start Notera now is unobtrusive as it runs in the
background, does not show *any* output, and does not block the terminal
it was started in (i.e. the terminal window can be closed and Notera
will keep running). The previous `npm start` (which produces output and
is stopped by pressing `CTRL-C`) is now achieved via `npm test`, as it
should be a one-only test after the initial download to verify that
Notera indeed runs as expected.

In addition, stopping, restarting and updating has been made simpler
with `npm` based commands in all cases.
docs($update,$install): simpler update method

Also replace mentions of `npm start` with `npm test` in $install.
style($config): Switch from js module to json data format

This is preferable to the previous state of having `module.exports = `
at the beginning of the configuration file because not only is it
shorter and hence simpler and cleaner, but more importantly, it is less
confusing for end users. `module.exports =` at the beginning of the file
is a mystery to them since they do not know what it does and would most
likely be told to ignore or leave it be even though the configuration
file is *theirs* to edit.

The loss of comments in the configuration files is not a problem since
the documentation should cover explanation of the configuration options
anyway. Although it would have been nice to explicitly refer to the
existence of explanation of options in the documentation from the
configuration file itself.
docs($install): put final installation command on separate line

This more clearly shows that there are three main installation commands
at a glance and hence it is more readable to the user as an important
and explicit instruction.

Also add link mentioning the ability to download the latest
*development* release as a `.zip` file (rather than being forced to `git
clone` as seemingly previously suggested).
fix($search): search result excerpts extract the correct section

The excerpts were sometimes incorrect due to this incorrect conditional
(in `host/query.js` when attempting to determine the start and end
points of each result's excerpt).