[evolution] evolution of class place, the object of field only accepts a window, other options, such as fixed, percent and room, are all deprecated, these options are all should be defined in div-text.

place.field("div")<<place.fixed(wgt1, 10)<<place.fixed(wgt2,20)<<wgt3; //deprecated

place.div("<div arrange=[10,20]>"); //new div-text arrange.
place.field("div")<<wgt1<<wgt2<<wgt3;
Bugfix: wrong token returned by place tokenizer
feature: place supports min/max to limit a div range, a qPCR4vir's feature
feature: place supports the initial weight of the field in right side of splitter. A qPCR4vir's feature.
feature: Added place::erase() method to erase a window. And qPCR4vir's pull request.