Basic drawing functionalities

[BlackFoundry]

Built-in:

• [x] #857
• [x] #365
• [x] #684
• [x] #360
• [x] #247
• [x] #248
• [x] Ability to select a full contour simply (done in #275, and #294)
• [x] #295
• [x] Convert line to curve #302 #320
• [x] Convert curve to line (by deleting handles)
• [ ] #627
• [x] Copy / Paste contours (within one glyph or between 2 different glyphs)
• [x] Copy / Paste from / to external applications #260
• [ ] Align selected point (H or V)
• [x] #264
• [x] #265
• [x] #268

Plug ins:

• [ ] Nudge tool
• [ ] Advanced measuring tool
• [ ] Highlight misaligned segments (almost vertical / horizontal)

[justvanrossum]

Some of the above will be much easier to implement once #239 and #254 are farther along.