New IncDec plugin for Geany

[scresto09]

IncDec is a plugin for Geany that provides shortcuts to increment an decrement number at the cursor, or to the right of the cursor (on the same line).

By default, typing Shift-+ will increment the next number, and typing Shift-- will decrement the next number. You can also increment and decrement number many times by typing **Shift-*. The number can be at the cursor, or to the right of the cursor (on the same line). Numbers can be negative and positive, and can be in decimal or hexadecimal format (hexadecimal number start with 0x**). You can customize those defaults keys on the preferences, under the Keybindings tab by setting the IncDec keybinding. An item Increment or Decrement number is also added in the Editor Popup Menu, it can be hidden by changing the Plugins Preferences.

[scresto09]

This pull request replace previous #1337