blueman-adapters: Remove leftover call to SetProperty

Also make the name entry insensitive and add FIXME for now as the
property is readonly in BlueZ5.
Github issue: https://github.com/blueman-project/blueman/issues/104
update Arch Linux package link

Closes #106
Allow debug output when running as subprocess

If the blueman process itself does not control a STDIN and the system call to get its group ID fails, check if the DEBUG variable is set instead of always assuming a background process with no output.
Update about dialog

Closes #47
Use Alias property as adapter name if present

Closes #104
Remove custom passkey function from pairing dialog
Release agents when unloading the AuthAgent plugin
Reformat NMDUNSupport and PPPSupport
Check for required icon themes.

We can use either gnome or mate icon theme but we need one.
Add icon theme requirements
Functions: Implement our own which logic in have() function.

On distributions sbin is usually not in the users PATH and we fail
to detect dhcpd(3) and/or dnsmasq.

The have() function now uses our own which implmentation and
adds both /sbin and /usr/sbin when reading PATH. It will now return
the the full path when found or None if not.

Also update NetConf.py to use the updated have() function.
Support both dhcpd and dhcpd3.
Add back import for Popen

Accidentally removed in ce13c7d6203325a80859cac5475ad45497eb1eb6
NetConf.py: import have from Functions

Forgot to commit..
NetUsage: Replace forgotten call to ListAdapters()
Add which / have changes to changelog
Actually use custom status icon

Closes #86