Allow to change the font size from keyboard/mouse

Closes #46 (closed) and #54 (closed), depends on !46 (merged).

This MR first refactors a bit the code around MousepadView properties:

• replace "font-name" with "font" ("font-name" is deprecated as GtkFontButton property since 3.22, and quite confusing since it's actually some kind of font description);
• make properties only writable, since it's the only way they are accessed in the code;
• clarify the way the font is set, depending on whether the default font is used or not.

Then, a little commit adds the ability to increase/decrease the font size from a keybinding (Ctrl +/- by default), or using Ctrl + mouse wheel.

I chose to make this font size change temporary, and only apply to the active view, a bit like Gedit does (although here, a change of font settings reset this temporary change). If we ever want to change that, it won't be a big job.

added 1 commit

• 53e6f23c - Allow to change the font size from keyboard/mouse

Compare with previous version

Useless cast.

mentioned in merge request !62 (merged)

added 40 commits

• 53e6f23c...c39b5ad9 - 38 commits from branch apps:master
• 5d0a5d86 - Code refactoring around MousepadView properties
• afa94c95 - Allow to change the font size from keyboard/mouse

Compare with previous version

merged

Since this MR the first line of the document is slightly cut off at the top.

mentioned in commit dd81bf02

resolved all threads

mentioned in commit 005c6907

mentioned in commit d93cb42e

changed milestone to %0.5.1