[keepalive] Provide an instantiable KeepAlive class. Fixes JB#23308

The Keepalive was accidentally made into shared singleton object
instead of instantiable class. Which means that if a qml application
is using KeepAlive from several places, they will interfere with
each other.

Make instantiable KeepAlive class available to new code that imports
org.nemomobile.keepalive 1.1.

The existing is org.nemomobile.keepalive 1.0 retained for the sake
of backwards compatibility.

Signed-off-by: Simo Piiroinen <simo.piiroinen@jollamobile.com>
Make examples use org.nemomobile.keepalive 1.1

No other changes except KeepAlive is now class instead of global
object.
Fix unique id string generated by BackgroundActivity class

It does not really matter what the string is as long as it is unique
within the process. But "KeepDisplayOn" is logically incorrect and can
cause confusion if/when it ends up in system logs.

Use "BlockSuspend" instead.
Fix problems when running qml examples with qmlscene

When the example qml applications are executed with qmlscene, there
are warnings emitted to console, wrong fonts are used in ui, checked
glare is missing from TextSwitch objects, etc

Use Component wrapper for initialPage.

Also, since the indentation level changes anyway, use uniform
indentation across all the example code.
Merge pull request #4 from spiiroin/jb23308_keepalive_class

Provide an instantiable KeepAlive class
Bump nemo-keepalive version to 1.2.0