Simplified dispatcher, templates, etc

tldr version: 'The Latest Posts' view works as expected, with fewer lines of
code.

Long version:
I turned to a system of global variables that control things, while other
files are selectively included. This makes my job easier without silly stuff
like objects. With a small set of globally-available variables, I can do all
that I need to.

Templates will be redone, but I need to do a few more pages before I decide
how it needs to be done. Right now the only template is the main template used
for the blog layout. Developing this won't be easy.

The pager was also updated to fit in with the new variables.
Converted Profile Editor, corrected previous omission of file deletion
Update login error handling
Update Page Editor, tidy up variable use somewhat
Update single page view

Also added edit and delete buttons to the single page view
Add edit and delete functionality to the "latest" view

* Turned sb_pagecount into sb_count, anticipating further
  need for it in the management sections.
Check for PHP version, SQLite3, and permissions
Site Editor converted and improved

* Profile and Site Editors were revamped to be cleaner
* Stylesheet was improved to better support zooming
* sb_version_check() now accepts a minimum PHP version to check for
Converted Page Manager, fixed Latest view

* Updated README
Protected the page editor from SQL injection
All functionality now matches 'master' branch

Merging into 'master' is on the agenda.
All views work as expected

* Removed an old, broken file (site_stats.php)
* Generalized the page list view
* Fixed a bug when trying to add a page
Changed all calls of date() to strftime()
User creation now possible

* Fixed $USERINFO issues
* Fixed logic issue with searching for pages by an author not returning
  matches and displaying a "user not found" error instead.
Fixed cascading issues with tags, pages, and users

* Fixed tag display logic
* "Pages" and "Sections" now only appear in the navbar if there are pages or
  tags that need to be displayed.
Basic commenting now working

Lots of work yet to be done on commenting. For now, it processes comments
with Markdown. This will suffice for most things. htmlentities() is used on
all comments, so scripting attacks aren't possible. If Markdown won't render
it, it can't happen.

I'm still displeased with it, but it works and the codebase is due for
clean-up as soon as I'm done with the Atom feed generator and search
engine. I'll save the refining until then.
Comment system mostly done

* Referring to comments via @xxx syntax works
* Usernames case insensitive upon login
* Stylesheet updated for comment elements
Assigning tags now case insensitive

There was a problem with extra tags being created if their case didn't match
the one in the database. That's correct, but undesired behavior. Now if you
enter a tag on the page creation screen that's not matching in case, it'll
still be detected as an existing tag and associated with it instead of
creating a new one.

Yay for efficiency!
Fix post and tag editor regressions

Also added more plans to TODO
Corrected Tag Manager quirk

* Styled the pager <p> element.
* Updated the license to include Non-Commercial clause.