1. Added more position option for AddImageWatermark: center, top-center, bottom-center, center-left, center-right

2. Add AddTextWatermark client action, easily write text on top of image.

Fix: 

- Now only resize larger resolution image (compared to MaxWidthOrHeight input parameter)

- fix orientation still applied for smaller image

Minor clean up...

Update:

- if image input = NullBinary() (empty image), no longer raise exception

- FixOrientation: input parameter "orientation" is optional now (was mandatory).

if input parameter "orientation" is empty or "0", orientation will be automatically acquired (only source binary data with EXIF info).

- AddImageWatermark: now has 2 additional output parameters to eliminate the need to raise exception

- success (boolean)

- errormessage (text)