Update fyne to v2

[ersonp]

Fixes #

Changes:

• Updated fyne to v2
• Changed depreciated functions
• Changed from github.com/lucor/fyne-cross to github.com/fyne-io/fyne-cross

Does this change need to mentioned in CHANGELOG.md?

No

[jdknives]

Running into /

usr/bin/docker run --rm -t -w /app -v /home/work/go/src/github.com/skycoin/skybian:/app -v /home/work/.cache/fyne-cross:/go -e CGO_ENABLED=1 -e GOCACHE=/go/go-build -e GOOS=linux -e GOARCH=amd64 -e CC=gcc -e fyne_uid=1000 lucor/fyne-cross:1.5.0 go build -ldflags ' -w -s' -o /app/fyne-cross/bin/linux-amd64/skyimager-gui -v ./cmd/skyimager-gui
build github.com/skycoin/skybian/cmd/skyimager-gui: cannot load embed: malformed module path "embed": missing dot in first path element
Could not build for linux/amd64: exit status 1
make: *** [Makefile:63: build-skyimager-gui] Fehler 1

[mrpalide]

New Changes:

• [x] Add simple cache process to reduce getting image base urls from github
• Change working directory from a simple text field to folder chooser by click on it
• Cancel button not work during download base image

[jdknives]

New Changes:

• Add simple cache process to reduce getting image base urls from github
• Add a button to reload urls more than once manually
• Change working directory from a simple text field to folder chooser by click on it
• Cancel button not work during download base image

@mrpalide some good ideas but not relevant for now. Please do not implement features that are not requested or were not implemented before. Please get the download cancel working button working and make the tests pass. Cache and URl reloading was not supported previously iirc.

[alexadhy]

For cancel button:

Can't we just spawn another window in fyne ? then just add that progress bar and that cancel button to it, while disabling forms and button on the first window? just an idea

since that cancel button will not be called until after the progress bar finished, from the callstack, and that's I believe is the issue from the library itself the issue is the Download function is blocking UI event thread from running.

Since there's not a lot of differences between decoration-less Window and dialogs, I made it work with SplashWindow (mine is a 15 minutes bad hack)

dialog.mp4