Update and fix Strings stringToTime()

Allow parsing of more flexible interval strings including
long names (day, hour, minute, second, millisecond),
negative values, no spaces between components, and
throwing exceptions on invalid input if requested.

The following types are now allowed
- d|day|days
- h|hour|hours
- m|min|mins|minute|minutes
- s|sec|secs|second|seconds
- ms|msec|msecs|msecond|mseconds|millis|millisec|millisecs|millisecond|milliseconds

Also fix the milisecond parsing that was done completly wrong
the milliseoncds where just added after a "." as decimals without converting them at all.
Now the value is divided by 1000 and added to the existing number, and as before only if ms exist

The negative check is now included in the main parse regex, so a second regex check is no longer necessary

Spaces between values, before or anywhere are now more flexible.

Exceptions are thrown if the regex cannot parse anything, or it returns only one master entry and no matches

www/admin/class_test.datetime.php

@@ -225,6 +225,36 @@ foreach ($intervals as $interval) {
 	print "STRINGTOTIME: $reverse_interval: " . DateTime::stringToTime($reverse_interval) . "<br>";
 }
 print "<hr>";
+$interval_strings = [
+	'10d 5h 30m 15s 123456ms',
+	'18999d 0h 38m 10s 1235ms',
+	'18999 d 0 h 38 m 10s 1235ms',
+	'-2h 15m 5s',
+	'45s 500ms',
+	'0s',
+	'0ms',
+	'1s 5ms',
+	'1s 50ms',
+	'1s 500ms',
+	'1s 5000ms',
+	'10day 5hour 30min 15sec 123456millis',
+	'10day 5hour 30min 15sec 123456millisec',
+	'10day 5hour 30min 15sec 123456msec',
+	'-2days 3hours 15minutes 30seconds 250milliseconds',
+	'',
+	' ',
+	'invalid',
+];
+foreach ($interval_strings as $interval_string) {
+	print "STRINGTOTIME: $interval_string: " . DateTime::stringToTime($interval_string) . "<br>";
+	try {
+		// test exception
+		DateTime::stringToTime($interval_string, throw_exception:true);
+	} catch (\InvalidArgumentException $e) {
+		print "ERROR: " . $e->getMessage() . "<br><pre>" . $e . "</pre><br>";
+	}
+}
+print "<hr>";
 $check_dates = [
 	'2021-05-01',
 	'2021-05-40'