Rixstoolbox

* several small, GUI related bug fixes

* fixes several bugs in v0.6.1, most of them due to changes in the API of PyMca after migration to silx
* small changes in the background subtraction options in the tool for image-to-spectra reduction

Windows:
You can use the provided installer to install RixsToolBox. Alternatively, you could download and unpack the ZIP file into a folder and then run "RixsToolBox.exe" located inside the folder.

MacOS:
Download and unpack the ZIP file into a folder and then run "RixsToolBox.exe" located inside the folder using Wine.

* added support for Diamond Light Source I21 data format (single- and multiframe images)
* added support for using dark images for background subtraction
* changed to Python 3.6, PyQt5 (was Python 2.7, PyQt4)

Binaries should also run under MacOs X and Linux using wine.

SpecGen tool has been thoroughly tested; the other tools less so. If you notice a bug please open an issue or send a mail. If the program crashes you should see an error message in the shell window that is opened when you start the program. If you can copy this message and paste it into your mail/issue.

For the moment only SpecGen tool. Entry point is "RTB_SpecGen.exe" located in installation folder. Binaries should also run in Wine on MacOS X and Linux.

* added support for Diamond Light Source I21 data format (single- and multiframe images)
* added support for using dark images for background subtraction

The generated *.spec output files can be further analysed using one of the older releases.

<h3>Installation</h3>

**Windows 7/10 (64bit)**

Download and use the provided installer `RixsToolBox-0.5.1-x64.exe` to install and uninstall RixsToolBox comfortably.

Alternatively you can also download and unpack `RixsToolBox.v0.5.1.zip`. Then start `RixsToolBox.exe` which is located inside the main folder.


**MacOS X**

Download and unpack `RixsToolBox.app.zip` and copy `RixsToolBox.app` into the `Applications` folder.

Added "Align to trend" and "Use sum as reference" options to SpecSum