Do not mess up page content with leading slashes.

If a page title started with a slash, the algorithm to deal with leading
capitals would produce a faulty regexp by accessing $escapedTitle[0] and
substr($escapedTitle, 1), which would only capture the slash that escapes
the slash.

Also fix small bug in template detection (make expression non-greedy).
Prevent linking inside preformatted text and code.

Ignore lines that start with a space as well as text enclosed in <nowiki> or
<code> tags.
Add version 2.3.0 information.