Make guake use the system default theme and hide tab bar when there is only one tab

[Davidy22]

Detect system theme by default like other gtk programs. Some misc setup/cleanup changes in the fork as well.

[Davidy22]

I should have made a seperate branch for this, but I also did a little hacking and got a thing that should resolve #924 as well.

[jacksongoode]

Yes! I was just about to propose hiding with a single tab - nice. But who knows when this will get merged... This project really needs to hand off management.

[Davidy22]

Hiding with one tab was a resolution to an existing issue report, so someone else beat you to the punch by some amount already. I wouldn't mind taking the project up if needed, it has been a while since I made this pull request and there's a lot of other pull requests in the queue

[mlouielu]

Hi @Davidy22, please help to change a branch from your master branch to another name, otherwise it may confuse to others.

[mlouielu]

We can separate this PR into two (or three), as we would like to have one purpose in one PR:

1. Add option to hide tab bar when we have only one tab
2. Make Guake use system default theme
3. Cleanup some code.

[Davidy22]

Alright, just gonna do some name shuffling and push some commits around. Been a while since I wrote this, but I think the cleanup was somewhat related to the themes feature