UI improvements and clipboard mode

UI

• swing will now use the default system look and feel
• the entire text will be displayed in a field at the top of the result window, where it can be copied from (to e.g. paste it into jisho.org directly)

Clipboard

• added the ability to translate the text directly from the system clipboard
• this can be done with the -c1 and -c2 (linux only, selection clipboard) flags
• these will display the results in the center of the screen