[voicecall] Remove pulseaudio and resource policy plugins.

These have not been installed by default, and have since been replaced by
functionality in ohm.
[voicecall] Fix uncallable DBus function.

Methods marked as Q_INVOKABLE are not callable over the DBus interface.
Make resetCallDurationCounters() a slot like all the other DBus
methods.
[voicecall] Add missing providers.pro
Merge pull request #17 from amccarthy/master

[voicecall] Fix uncallable DBus function.
Merge branch 'master' of github.com:nemomobile/voicecall