Move Encoding class away from the Language namespace

Language\Encoding::__mbMimeEncode -> Convert\MimeEncode::__mbMimeEncode
Langauge\Encoding::checkConvertEncoding -> Check\Encoding::checkConvertEncoding
Langauge\Encoding::setErrorChar -> Check\Encoding::setErrorChar
Langauge\Encoding::getErrorChar -> Encoding::getErrorChar
Langauge\Encoding::convertEncoding -> Convert\Encoding::convertEncoding

Also fixed encoding check that not only a code point but a string can
also be used as a parameter.

Update phpunit tests and split them out for each class

Normal test page is still combined for all classes but updated to
correctly use each class

www/lib/CoreLibs/Convert/Encoding.php

@@ -0,0 +1,60 @@
+<?php
+
+/*
+ * check if string is valid in target encoding
+ */
+
+declare(strict_types=1);
+
+namespace CoreLibs\Convert;
+
+class Encoding
+{
+	/**
+	 * detects the source encoding of the string and if doesn't match
+	 * to the given target encoding it convert is
+	 * if source encoding is set and auto check is true (default) a second
+	 * check is done so that the source string encoding actually matches
+	 * will be skipped if source encoding detection is ascii
+	 *
+	 * @param  string $string          string to convert
+	 * @param  string $to_encoding     target encoding
+	 * @param  string $source_encoding optional source encoding, will try to auto detect
+	 * @param  bool   $auto_check      default true, if source encoding is set
+	 *                                 check that the source is actually matching
+	 *                                 to what we sav the source is
+	 * @return string                  encoding converted string
+	 */
+	public static function convertEncoding(
+		string $string,
+		string $to_encoding,
+		string $source_encoding = '',
+		bool $auto_check = true
+	): string {
+		// set if not given
+		if (!$source_encoding) {
+			$source_encoding = mb_detect_encoding($string);
+		} else {
+			$_source_encoding = mb_detect_encoding($string);
+		}
+		if (
+			$auto_check === true &&
+			isset($_source_encoding) &&
+			$_source_encoding == $source_encoding
+		) {
+			// trigger check if we have override source encoding.
+			// if different (_source is all but not ascii) then trigger
+			// skip if matching
+		}
+		if ($source_encoding != $to_encoding) {
+			if ($source_encoding) {
+				$string = mb_convert_encoding($string, $to_encoding, $source_encoding);
+			} else {
+				$string = mb_convert_encoding($string, $to_encoding);
+			}
+		}
+		return $string;
+	}
+}
+
+// __END__