miscellaneous improvements to packrat new project option

- save and restore the last value of "use packrat with this project" as a UIPref
- pass the progress indicator to the bootstrap rpc call so the step's progress is auto-dismissed
- locate git and packrat checkboxes on the same line so they always fit vertically
- tweak the git and packrat checkbox text
merge commit

Merge branch 'feature/packrat-integration' of github.com:rstudio/rstudio into feature/packrat-integration

Conflicts:
	src/gwt/src/org/rstudio/studio/client/projects/Projects.java