"Edit" button to edit existing textblocks

[GeorgeCiesinski]

Description:

Add a button to edit existing textblocks

Solution:

1. An edit button is placed on the root window under the textblocks display. Clicking this checks to ensure a textblock has been highlighted in the textblock window. If yes, it opens a toplevel widget with:

• (Is this needed?) A dropdown list containing the directories setup in the config file & label naming the dropdown
• A text input field for the shortcut & label naming the text input field. This will contain the existing shortcut and cannot be edited (greyed out)
• A text input field for the textblock & label naming the text input field. This will contain the existing textblock and can be edited.
• A save button

2. Clicking save checks if any change has been made. If yes, it overwrites the existing file in the selected directory.
3. Automatically reload textscript.

[GeorgeCiesinski]

Added toplevel widget in commit 5fe1d97