Reportlab2

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* update travis version of multibuild contrib by Matthew Brett
* fixes to cope with python 3.9
* imrove Drawing formats handling and ensure asString can do svg

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* test fixes
* Label enhancement
* added isSubclassOf validator
* added CrossHair widget

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* attempted restriction of the reportlab.lib.color.toColor function

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* fix bug in Pie3d reported by Eldon Ziegler <eldonzatlanticdb.com>
* fix bug in background splitting in repeatRows cases reported by David VanEe <david.vaneeconvergent.ca>
* small improvements to CandleSticks
* created NotSet validator (use in CandleStickProperties)
* update .travis.yml and .appeyor.yml hopefully to create 3.8 wheels

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* some chart efficiency changes
* use clock in fontFinder contributed by Matěj Cepl bitbucket
* improve recursive access and do some minor eval/exec fixes
* improve use of eval/exec

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* paraparser fix contributed by ravi prakash giri <raviprakashgirigmail.com>