3.0b3

[azazellochg]

• update GH action
• update docs with installation prerequisites
• improve docstrings / documentation
• pillow is no longer optional
• imageio is optional
• new property: is_flashing_advised
• focus_index renamed to gun_lens
• for vector attrs allow to set from a list or tuple
• fix tecnaiccd image orientation
• add a doc about acquisition
• set default camera size for STEM
• stem rotation reported in degrees
• stem fov is read only
• use enums for aperture names
• probe defocus and conv angle are read-only
• rename acquisition.screen to screen_position
• few fixes for python 3.4