Variables in Repo directory and resizable repo/clone dialogs

[mattcasters]

This allows us to package up projects completely self-contained and auto-configured using kettle-environment by setting the repo directory to something like ${ENVIRONMENT_HOME}

[mattcasters]

It was barely usable on my 4k screen Hota-san so I started rewriting it. A for the realDirectory, it was really confusing to figure out which directory was the right one it being spread out over the dialog and GitRepository. I also wanted to have an identifiable method to replace later when we support Kettle Environments perhaps since this is one of these cases where System.properties is used to store Environment settings. Ultimately I don't care about the code-change either just about the results. If you feel there's a better way than feel free to do as you see fit :+1:

[mattcasters]

By the way, it's not just having the ability to resize, it's also remembering the last size. There is nothing more painful when you use multiple screens to see a tiny dialog smack in the middle of 2 screens or somewhere strange to have to drag it to where you're working and then resize it (and seeing it's not possible), not being able to see the options clearly (tiny dialog on a high resolution screen) and then to redo this every time you use the dialog. So the fix you mentioned solves resizing but not the rest. Cheers!

[HiromuHota]

I separated out changes for #24, #26 & #27, respectively. I'd like to merge the changes for #23 too, but let me consider it from the implementation point of view.