Add linear referencing functions.

Add functions to project points onto lines and paths.
rename line.Project to line.ProjectionFactor
Update comments, ordering for linear referencing functions.
Rename projection methods on lines and paths:

line.ProjectionFactor -> line.Project
path.Project -> path.Measure
path.ProjectNormalized -> path.Project
Merge pull request #1 from bdon/master

feature proposal for projecting points onto lines/paths