Fix bugs in PNG uploading and add textboxes.

[alexanderdna]

Hi. I have been using your Particle2dx tool for creating particle effects for cocos2d-x games. While using it I found some issues and the following are what I have changed. I hope you don't mind.

• Uploaded PNG file can only be selected once. Fixed so that it can be
  reselected.
• Some fields have no textbox to enter exact value. I added the
  corresponding textboxes for these fields.
• Changed all <? to <?php for compatibility reason.
• Fix some small bugs.

[mash76]

thank you !
now, source code on github is out of date from particle2dx.com . so I will cherry picking & merge manually.

[sedjamal]

Hi
The png files are very few, I can add some more to make more options, especially all of them have white color as basic so on some backgrounds it doesn't make good results.