Merge pull request #3 from adenexter/master

Fix display of thumbnails with fillMode: PreserveAspectFit.
[qmldir] Add Module Identifier Directive
[nemo-qml-plugin-thumbnailer] Allow use in auto tests

Auto tests can instantiate the QML engine repeatedly without halting
the QApplication.
Merge pull request #5 from matthewvogt/auto-tests

[nemo-qml-plugin-thumbnailer] Allow use in auto tests
Merge pull request #4 from thp/module-identifier-directive

[qmldir] Add Module Identifier Directive
[nemo-qml-plugin-thumbnailer] Use non-opaque texture material.

QSGOpaqueTextureMaterial limits usage to fully visible state.
Merge pull request #6 from pvuorela/master

[nemo-qml-plugin-thumbnailer] Use non-opaque texture material.
[nemo-qml-plugin-thumbnailer] Fixed a crash when creating thumbnails from large images.
Merge pull request #7 from zchydem/master

[nemo-qml-plugin-thumbnailer] Fixed a crash when creating thumbnails from large images.
[nemo-qml-plugin-thumbnailer] Fix borders on thumbnails.

Centering a 180x180 rectangle around a point at 90x90 gives a rectangle
with the top left at (1,1) not (0,0) so the crop rectangle ends up
slightly outside the bounds of the image.  Biasing the width and height by 1
when dividing to get the center gives a 1x1 negative offset necessary to
get the correct center for even sizes without overcompensating for odd
widths.