Remove unused files and directory in the sources.

[jujudusud]

Identifying some directory and some files that are no longer used for the app.
It's located in : jamulussoftware/jamulus/src/res/homepage/

I'm will create a PR for that as soon as possible.

[vimpostor]

Another thing that I found that needs to be cleaned up is that multiple source files somehow have the executable flag set.
Something like find src/ -type f -exec chmod -x {} \; should to the trick.