Create jquery.clearField.js

Taking some elements from jquery.clearable.js and the structure from http://www.sitepoint.com/10-tips-better-jquery-plugins/.

Adding some function to what jquery.clearable did:
* Auto hide clear-button when empty value
* width change option: to make the input bigger when the clear "button" is added
* top and right options insted of fix them thru css
* customizable title text (clearText).