Optimize undo/redo hotkey: support shift and adapt to mac os

Changes:

• Optimize undo/redo hotkey: support shift and adapt to mac os
• Add 'AboutDialog'

It's still compatible with jdk6

Adapt to java11 & use maven & add some functions

Changes:

• add function 'Hole', for skillful usage
• add function 'Length', for getting string's length
• 'com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel' was removed in new jdk version, so make it compatible
• convert to maven project
• move packages to 'com.github.trytocatch'

It's still compatible with jdk6

Fixed a cache bug

fixed a bug:incorrect use of cache in FuncNode

Add new function 'DynRepeat'

Add new function 'DynRepeat':

• repeat the string for several times with the max length
• read the new value for the first argument at each repeat
  read the help doc in software for more details.

Add new function 'Repeat'

Add new function 'Repeat'