Main Tab UI - Changes

[mpatrou]

The code has the following
Updates:

• A new field is added in Histogram Parameters section labeled: 'Intensity'. It contains minimum and maximum values. Neither, both and one of them are allowed. The values are used to set appropriate limits for 1D, 2D, 3D and 4D plots.
• Display titles for 1D and 2D plots are updated to include min and max values of the corresponding dimensions.
• Progress Bar is updated when loading files.
• Load Buttons are reordered

Code restructures:

• invalid styles are imported everywhere the same

Minor Bug fixes:

• Oncat directory schema check

Additional tests are included.