Was using classes to define tools, however this makes it awkward to
dynamically generate them (we can do it, but its not very "Pythonic").
Move to a named tuple.
Originally it was nice to have a small list of definitions
with tools inline.
However we need to be able to define drawing functions for tools
which Python can't easily inline.
Use function for keymap definition,
support creating a function from a tuple as well
(handy for simple key-maps).
Add the 3D view ruler as a tool,
the modal operator remains for now
however it may be removed if we use the tool-system for 2.8.
Note that this does copy code from the operator,
its different enough not to attempt to de-duplicate.
Tool for creating polygons, exact usage may change based on feedback.
LMB to add faces at boundaries (tris from edges, quads from verts).
- Ctrl splits edges
- Alt to dissolve edges/verts.
Works well with vertex snap & auto-merge.
This uses selection hover but isn't intended to introduce more widely
pre-selection highlighting, at least it will be restricted to this tool.
The tool-system it's self is primitive and may be changed.
Adding to 2.8 to develop operators and manipulators as tools.
Currently this is exposed in the toolbar, collapsed by default.
Work-flow remains unchanged if you don't change the active tool.
Placing the 3D cursor is now a Click instead of a Press event,
this allows tweak events to be mapped to tools such as border select,
keeping click for 3D cursor placement when selection tools are set.
