Rebrand app to Dsub2000

[norohind]

Advances #5
This PR changes app id from github.daneren2005.dsub to github.paroj.dsub2000. As a side effect, ServerProxy's id was changed from github.daneren2005.serverproxy to github.paroj.serverproxy.
Where I could, I changed name of the application in strings which are shown to end user.
I tested my everyday scenarios of using this app and everything seems to work just fine. I also tested DLNA casting - good.

After this, new builds will install alongside with old application. Thus not updating it and not preserving/migrating user settings/cache from old application. Here's how I migrated my settings and cache to new application (root is required):

1. cp -r /storage/emulated/0/Android/data/github.daneren2005.dsub/* /storage/emulated/0/Android/data/github.paroj.dsub2000/
2. rm -rf /data/user/0/github.paroj.dsub2000/*
3. chown -R u0_a509:u0_a509 /data/user/0/github.paroj.dsub2000/ # Make sure to adjust owner
4. cp -r /data/user/0/github.daneren2005.dsub/* /data/user/0/github.paroj.dsub2000/
5. And then manually replace demo server with your own in settings
6. Manually set desired cache size in settings
7. Manually check other settings is set to desired values (settings seems to be completely lost during migration, but I'm not sure)

As result, songs cache is preserved, it was most important for me.