Renderer upgrade

[ThomasKroes]

Aim of the PR

The primary objective of this PR is to use all the screen estate in 2D point and density-based renderers. Previously, due to square rendering constraints, rendering space was not always used optimally. This PR solves that problem, along with some overdue partial overhaul of rendering base classes.

Requires this scatterplot plugin PR for full review.

Newly introduced classes

• mv::Renderer2D, a rendering base class that generalizes common 2D rendering and interaction behavior. It has a navigator for interacting with the camera and contains helper functions to switch between coordinate systems.
• mv:Navigator2D, a helper navigator class for navigating within 2D renderers. Objects of this class are coupled with a source renderer widget for which it takes care of all mouse events.
• mv::NavigationAction, a generic action class with a commonly used GUI for 2D and 3D navigation in renderers
• mv::gui::NumericalPointAction, a numerical base class action for point actions
• mv::gui::IntegralPointAction, a point action class for integral points, derived from mv::gui::NumericalPointAction
• mv::gui::DecimalPointAction, a point action class for decimal points, derived from mv::gui::NumericalPointAction

Other changes

• Added zoom to selection
• Added zoom to window
• Fixed randomized depth reseeding issues
• Added icon modifier API in mv::util::StyledIcon
• Re-instated size override hints in mv::gui::WidgetAction
• Rectangle actions are moved to the actions/numerical source group
• Removed redundant image renderer
• Checked shortcuts
• Removed some virtual + final constructions here and there

[alxvth]

Rebased to fix CI build so that ManiVaultStudio/ExamplePlugins#42, ManiVaultStudio/Scatterplot#173 and ManiVaultStudio/ImageViewerPlugin#146 build fine