ARROW-1937: [Python] Document nested array initialization
ARROW-1937: [Python] Document nested array initialization

Author: Antoine Pitrou <antoine@python.org>

Closes #1663 from pitrou/ARROW-1937-nested-array-init-doc and squashes the following commits:

b85d1b2 <Antoine Pitrou> ARROW-1937:  Document nested array initialization

icexelloss/arrow,pcmoritz/arrow,icexelloss/arrow,dremio/arrow,majetideepak/arrow,itaiin/arrow,majetideepak/arrow,xhochy/arrow,dremio/arrow,majetideepak/arrow,xhochy/arrow,apache/arrow,laurentgo/arrow,yufeldman/arrow,dremio/arrow,majetideepak/arrow,cpcloud/arrow,wesm/arrow,wesm/arrow,wesm/arrow,renesugar/arrow,majetideepak/arrow,itaiin/arrow,yufeldman/arrow,xhochy/arrow,laurentgo/arrow,majetideepak/arrow,pcmoritz/arrow,pcmoritz/arrow,apache/arrow,itaiin/arrow,wesm/arrow,majetideepak/arrow,wagavulin/arrow,itaiin/arrow,kou/arrow,apache/arrow,itaiin/arrow,icexelloss/arrow,kou/arrow,icexelloss/arrow,laurentgo/arrow,wagavulin/arrow,tebeka/arrow,renesugar/arrow,itaiin/arrow,wesm/arrow,pcmoritz/arrow,cpcloud/arrow,pcmoritz/arrow,dremio/arrow,yufeldman/arrow,kou/arrow,laurentgo/arrow,xhochy/arrow,laurentgo/arrow,kou/arrow,kou/arrow,renesugar/arrow,laurentgo/arrow,icexelloss/arrow,yufeldman/arrow,xhochy/arrow,wagavulin/arrow,renesugar/arrow,wesm/arrow,renesugar/arrow,itaiin/arrow,tebeka/arrow,pcmoritz/arrow,xhochy/arrow,xhochy/arrow,wagavulin/arrow,wesm/arrow,icexelloss/arrow,pcmoritz/arrow,wagavulin/arrow,dremio/arrow,wesm/arrow,majetideepak/arrow,kou/arrow,wesm/arrow,cpcloud/arrow,yufeldman/arrow,renesugar/arrow,apache/arrow,majetideepak/arrow,itaiin/arrow,pcmoritz/arrow,tebeka/arrow,kou/arrow,wesm/arrow,icexelloss/arrow,majetideepak/arrow,tebeka/arrow,renesugar/arrow,laurentgo/arrow,majetideepak/arrow,renesugar/arrow,majetideepak/arrow,yufeldman/arrow,pcmoritz/arrow,xhochy/arrow,wesm/arrow,laurentgo/arrow,cpcloud/arrow,laurentgo/arrow,kou/arrow,pcmoritz/arrow,laurentgo/arrow,renesugar/arrow,laurentgo/arrow,apache/arrow,kou/arrow,apache/arrow,cpcloud/arrow,cpcloud/arrow,wesm/arrow,pcmoritz/arrow,xhochy/arrow,renesugar/arrow,itaiin/arrow,wagavulin/arrow,kou/arrow,icexelloss/arrow,cpcloud/arrow,itaiin/arrow,wesm/arrow,wagavulin/arrow,apache/arrow,itaiin/arrow,xhochy/arrow,wagavulin/arrow,laurentgo/arrow,itaiin/arrow,tebeka/arrow,majetideepak/arrow,laurentgo/arrow,dremio/arrow,pcmoritz/arrow,renesugar/arrow,itaiin/arrow,apache/arrow,xhochy/arrow,renesugar/arrow,cpcloud/arrow,wagavulin/arrow,tebeka/arrow,apache/arrow,renesugar/arrow,xhochy/arrow,dremio/arrow,tebeka/arrow,xhochy/arrow,cpcloud/arrow,renesugar/arrow,kou/arrow,pcmoritz/arrow,kou/arrow,wagavulin/arrow,apache/arrow,icexelloss/arrow,pcmoritz/arrow,yufeldman/arrow,itaiin/arrow,dremio/arrow,renesugar/arrow,majetideepak/arrow,cpcloud/arrow,dremio/arrow,icexelloss/arrow,yufeldman/arrow,laurentgo/arrow,yufeldman/arrow,kou/arrow,icexelloss/arrow,apache/arrow,icexelloss/arrow,tebeka/arrow,wagavulin/arrow,cpcloud/arrow,cpcloud/arrow,yufeldman/arrow,cpcloud/arrow,dremio/arrow,apache/arrow,apache/arrow,icexelloss/arrow,tebeka/arrow,itaiin/arrow,wagavulin/arrow,wesm/arrow,dremio/arrow,tebeka/arrow,apache/arrow,yufeldman/arrow,xhochy/arrow,pcmoritz/arrow,kou/arrow,laurentgo/arrow,majetideepak/arrow,cpcloud/arrow,xhochy/arrow,icexelloss/arrow