DokuWiki assumes that the server's time is correct. Especially page
revisions and cache handling depend on correct time. If that's not the
case it can lead to problems later (as mentioned in #1644).

This patch adds a very simple time check using the Date response header
from the DokuWiki server to our do=check mechanism.

spelling fix

Using an HTML entitiy might be problematic in non HTML renderers or when
the output is escaped again.

array splice operations are expensive. when many cells in a table row
are missing, the operation should be executed only once instead for each
missing cell.

Default only text string exists, via localized translation a wiki admin
can add his/her own (html) version.

As discussed in Issue #1454 dokuwiki currently "forgets" additional
queryparams when redirecting from devel: to devel:start

Example:
https://www.dokuwiki.org/devel:?foo=bar
should result in
https://www.dokuwiki.org/devel:start?foo=bar
but actually results in
https://www.dokuwiki.org/devel:start

This commit fixes that behaviour.

Fixes #1454

with unittests

Now classes and data- attributes can be added to individual options

Let plugins add their own classes to builtin tables or lists.

Fixes #1188
Alternative for #1360 (and PR #1515)

This is required for the filelist plugin to fix issue #11 since $lastlevel became protected in "hrun".

RemoteAPICore
- visibility methods
- getAttachmentInfo returns modification date of deleted files
- pageVersions returns only current revision (once) if $first=0.
Adresses issue mentioned at #1550
- added unittests
- updated API number