Update alto-v2.1-draft.xsd
type definition xsd:string for attribute "CONTENT" of HYP element
MeasurementUnit - annotation change
EllipseType - annotation change and type definition
CircleType - annotation change and type definition
Consistent  data type definition for positions and dimensions

All xsd:ints changed to xsd:floats
First implementation #1
Merge pull request #2 from altoxml/v2.1-draft

V2.1 draft