Implements shortcut feature (related to #149)

[igorofc]

• Adds an additional field on the 'Search engines' section of the settings page for each engine, which will hold a single character to be used as a shortcut for that engine. This character can either be a letter, number or any other that doesn't require a modifier (e.g. Alt, Ctrl, Shift) to be typed.

• To activate the shortcuts the user has to check the option Use shortcuts for the search engines. Upon enabling this setting, another option named Always enable shortcuts will appear, which, if checked, enables shortcuts even without the popup showing up.

• Shortcuts don't work on editable fields.

• The user can control how the search will be carried out by selecting the opening behaviour under the option When using a shortcut.

• Additionally, the user can select the engine by using the TAB key and hitting Enter. In this case, the same opening behaviour used for shortcuts will apply.

[CanisLupus]

Hey Igor, thanks for the detailed write up. ;) I only began to look at your pull request today.

I noticed a problem. It seems that your commit "Implement shortcut feature" also includes all the changes from my last 7 commits, which will cause all of the changed lines to be attributed to you (as seen via the git blame command). Unfortunately this will make it hard to track the history and authors of the changed parts (both yours and mine).

Maybe you can tell me what you did here. :) It seems that in the process of joining all your changes into one commit (to fix the non-branched commits we've talked about before) you've also added all the changes from my newest commits, whereas they should have been merged afterwards. This would explain why the merge commit (76360f2b) actually only contains the small reordering of settings (thanks for that, btw!) instead of the usual "all changes", because Git saw no differences.

I really hate to ask this but do you have time to recreate the branch again (in whichever way you see fit) containing only your changes? :( The easiest way I see is to create a branch again from my current "develop" branch and just paste and overwrite the files you changed (the ones in this PR). Git should then only show you the things that actually changed, ready to commit. Of course this would compress everything into a single commit again, but the alternative would be to edit two old commits ("Implement shortcut feature" and the following merge) and I shudder to think what black magic of Git commands would achieve this.

Sorry that this process has been so complicated. At least now the README has a few notes about contributions, to hopefully help. I just intended to go through your code and suggest/make changes if applicable, but then I saw this. The rest should be much smoother!

Daniel

[igorofc]

Hey @CanisLupus. No worries. I'll recreate the branch. To be honest I don't know how it ended up that way. Maybe it has something to do with me trying to pull your latest changes - the new version you rolled out. Git still makes my head spin but I'm enjoying learning it so this counts as experience. Too bad this will only serve to spam your log though :).

[CanisLupus]

I see. :) On my end, no worries! Git is very complex and sometimes confusing, especially if you suddenly need to do something you've never done before. Even with a GUI sometimes it's bananas.

And thanks for recreating the branch!