Insert dummy text

Now the insert action inserts dummy text into the active field. This
dummy text will be replaced by whatever link the user chooses from
their library of bookmarks.
Lib window appears

Temp formatting on the window. Centred. Disappears when button is
clicked.
Container dims screen, styling added, close button working.

Container that dims the screen was added. The style was changed to make
it nicer, but still temporary. Close button is working.
GUI improved ... still need a logo

The GUI now displays all gifs as options to be selected, and inserts
the text when an image is selected.
Added Lazy loading

When you are inserting an image you it will load lazily. Recently
bookmarked images are updated in the library.
Minor update

Cleaned up some code, made the loading gif the correct size.
Removed bookmark name

Images are now added with a key: value pair of index# : url. index 0 is
reserved. There is no bookmark name. When inserting, images are
displayed by most recently added bookmark.
Auto removal of broken links

- Broken links are now removed automatically from the GUI and from the
backend.
- Cleaned up code a bit (changed some function names)
Merge branch 'feature_insertImage' into dev