QOfonoConnectionContext: Fix typo in property name

[libqofono] Fix QOfonoConnectionContext::IPv6Settings
Fix invalid uses of short ints with DBus

[libqofono] Fix QOfonoCallForwarding::voiceNoReplyTimeout
[libqofono] Fix QOfonoCallVolume::speakerVolume
QOfonoMessageManager: Fix typo in property name

[libqofono] Fix QOfonoMessageManager::alphabetChanged()
QOfonoMessageManager: Handle added/removed messages

I believe the slots onMessageAdded and onMessageRemoved has never been
meant to be public and nobody has used them outside of the
QOfonoMessageManager class.

[libqofono] Fix QOfonoMessageManager::messages
QOfonoSimManager: Fix getIcon()

[libqofono] Fix QOfonoSimManager::getIcon()
Add helper to safe compare variant values
QOfonoSimManager: Eliminate false change signal emissions
QOfonoSimManager: Handle modem power cycle

This actually fixes only one aspect of the issue - just to make it fit
the constraints defined by the current test cases (when they are fixed)
- wider refactorization should be done later to make the code more
robust and keep one approach among all libqofono classes.

[libqofono] QOfonoSimManager: Handle modem power cycle
QOfonoMessageWaiting: Eliminate false change signal emissions

This actually fixes only one aspect of the issue - just to make it fit
the constraints defined by the current test cases (when they are fixed)
- wider refactorization should be done later to make the code more
robust and keep one approach among all libqofono classes.
Tests: update tests for the current API

It also fixes many code indentation issues so I really recommend to
review changes with '--ignore-all-space' equivalent.
Tests: code polishing - use normalized signal signatures
QOfonoNetworkOperator: Remove recently added value semantics

Introduced with 856f137 ([libqofono] add auto tests.) in order to make
tests build possible. Hopefully nobody used it elsewhere and so it is
safe to simply remove it.
Fix memory leaks with QDBusPendingCallWatcher

This also refactorizes proper code to follow the same pattern of calling
watcher->deleteLater() at the very start of the callback (also good with
respect to callbacks with more than one return statement.)

[libqofono] Fix memory leaks on DBus calls
[libqofono] Don't change DBus properties unless they change.

If the local cached value of a DBus property is the same as the new
value don't bother sending the DBus command.
Merge pull request #38 from amccarthy/master

[libqofono] Don't change DBus properties unless they change.
Merge pull request #37 from martyone/master

Fix number of bugs, update tests for the current API
bump version to 0.53
[libqofono] Emit change signals when initializing QOfonoModem
Merge pull request #39 from pgerdt/fix-ofonomodem-signals

Emit change signals when initializing QOfonoModem
[libqofono] Correct property type.

The QOfonoModem::valid property was declared as type QString in
Q_PROPERTY when it is in fact a bool.