Code compatibility with CadQuery Editor

[roipoussiere]

This is now a meta issue that lists all steps required for CadQuery Editor compatibility:

• [x] #8
• [x] #34
• [x] #35
• [x] #36

[fpq473]

Highlighting some ways in which you may wish to match the CQ-editor experience:

• debug() is red with alpha 20% (you guesstimated 50% above): source

• There are several globals injected when running the code: source

• If show_object() isn't called then globals are searched for workplanes: source

[roipoussiere]

fixed in 09b0360