adding jamulus-server.desktop.in and new icons

[jujudusud]

In order to be in line with the comments made on #1605 , proposing this new pull request.
Fixes #1316

[softins]

I'm happy to add these for future use by packagers.

Do the files jamulus.desktop and jamulus.desktop.in also need attention? They are the same except for the Exec line, for which the latter has Exec=$$TARGET

[jujudusud]

You're right @softins ! Adding $$TARGET instead of Jamulus is the right way to do.
jamulus.desktop is generated when creating deb package I think.

[hoffie]

I think two further things should be done:

• The image files should probably be added to DISTFILES in Jamulus.pro, similar to jamulus.png
• jamulus-server.desktop.in should probably be added to DISTFILES and QMAKE_SUBSTITUES. The resulting jamulus-server.desktop should probably be added to dekstop.files in Jamulus.pro

(Note: I don't know specifics either, I'm just looking for similarities and what seems to be needed to make this useful)

[hoffie]

Thanks! This looks good to me.

Two (hopefully last) nits:

• After building this PR, the generated jamulus-server.desktop file looks good, but I think it should also be added to .gitignore similar to jamulus.desktop? (I think someone else -- @softins? -- had already pointed that out)
• One stray space, see inline comment

[jujudusud]

*it should also be added to .gitignore similar to jamulus.desktop?

Done by 48e837d

[hoffie]

Looks good to me. Sorry for the forth-and-back, I was unsure myself what other parts needed to be touched, but I think this lead to a good state now.

I'll defer merging for some days in case anyone else wants to have another look (@softins's review was about an earlier state, for example). Besides that, this is ready to go into 3.8.0, I think.

Thanks!

[softins]

Looks good to me now. Thanks!

[jujudusud]

Thanks !