js/CGP: Disable page refesh when scrolling or zooming a graph

When scrolling or zooming a graph we want to disable the page
refresh because we are trying to look at the detail. Unfortunately
Javascript cannot override the refresh meta tag;

<meta http-equiv="refresh" content="{$CONFIG['page_refresh']}">

Except with a window.stop() which is brutal but since the
complete RRD data has already been read this is not an issue.

See issue #139 suggesting submitting a PR to refresh RRD data
whilst a graph is scrolled or zoomed.

Move LICENSE to root directory

functions.inc.php: escape minus in regex

This makes CGP work on PHP 7.3 as it otherwise only shows an "Unknown
host" error message and logs the following PHP warning:

PHP Warning:  preg_match(): Compilation failed: invalid range in
character class at offset 4 in .../inc/functions.inc.php on line 37

Provide meaningful filenames for graphs

Readme: Reminder to allow .htaccess in vhost config

Gives decent default name when saving graph from browser as file and distinguishable tab for tabs showing graph.php output.

GenericIO: Fix negative_io for multiple instances

graph.php: Initialize $plugin_json variable.

When multiple instances are in one graph, every odd source must be negated,
not just the first.

Prevents error messages.

Fix for Invalid command 'RewriteEngine' when mod_rewrite is not enabled

Missing parentheses for LVM item name

The plugin was renamed in collectd 5.5.0.

It's finished :o)

Joking aside. It has been requested multiple times. So let's get it over
with. The last version was more then 3.5 years ago. This will be the last
tagged version of CGP. Every commit in the master branch after this
release can be considered as a new release. ;)

Use git and "git pull" to keep up-to-date or download the latest version
here https://github.com/pommi/CGP/archive/master.zip

Closes: #120 #143

When using "canvas" mode, a lot of these errors were thrown:
> Invalid type instance in $_GET["ti"]: ""
> Invalid type instance in $_GET["pi"]: ""

Closes: #132

Fixes:
> PHP Notice:  Undefined variable: html_weburl in inc/html.inc.php on line 131

Mentioned in #132
Closes: #141

fix array_search comparison

See http://php.net/manual/en/function.array-search.php for details why this is required.

Support for host categories based on regular expression matching

Closes #128

For example: "CPU Interface : 1" (snmp plugin + hp1810g switch)