optimize drag for mobile device

disable vertical drag if horizontal drag enabled for mobile device
optimize option $Looop
rename $JssorNavigator$ -> $JssorBulletNavigator$

$JssorNavigator$ -> $JssorBulletNavigator$
$JssorDirectionNavigator$ - >$JssorArrowNavigator$
$JssorNavigatorOptions - >$JssorBulletNavigatorOptions
$JssorDirectionNavigatorOptions -> $JssorArrorNavigatorOptions
caption rewind for slider with only one slide
reverse last check in
fix hardware acceleration for latest browsers
refactor skins, add new themes
jssor slider 15.0 release

jssor slider 15.0 release
with 6 more themes
rename themes to demos
new feature: add qr code to slider

see
demos\introduction-slider.source.html
demos\full-width-slider.source.html
fix api call '$GoTo'
improve lazy loading for nested slider
optimize custom attribute handling

attribute 'u' -> 'data-u'
change $PauseOnHover option default value to 1
minor changes for option configuration
file rename

rename demos\arrow-for-thumbnail-navigator-slider.source.html
to demos\thumbnail-navigator-with-arrows.source.html
update README.md, readme.txt
Improve $Loop option

0: stop, 1: loop, 2: rewind
improve $Loop option

patch for previous checkin
$Scale option bullet/arrow/thumbnail navigator

Add $Scale option bullet/arrow/thumbnail navigator