Adds projection angles load option

[dtasev]

Adds the option to load a projection angles file from the main window.

Also:

• Adds projection angles handling in images. Projection angles from logs are still top priority.
• Adds a simple parser for 2 formats of projection angles

The supported formats are comma separated or new-line separated:

0,0.1,0.2,0.3...

and

0
0.1
0.2
...

To test:

• Load a preview stack (only 11 images)
• To test either of the two formats copy and paste this into some file that you can select as a projection angle from File > Load proj angles
  • Test with/without a new line at the end.

0,0.1,0.2,0.3,0.4,0.5,0.6,0.7,0.8,0.9,1.0

and

0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0

• Try adding/removing angles. It should show an error with the number of each (angles provided and images available)

Fixes #674

[Pasarus]

Just a few comments, functionally it works great and is almost ready to be merged!