Add FAQ about InvalidModificationError

Provide info about InvalidModificationError due to symlinks in project.
add a dependecy library; add general decorator support
review comments
Added project type to analytics
Merge pull request #2892 from dart-lang/umop-analytics-project_type

Added project type to analytics
Merge pull request #2869 from devoncarew/devoncarew_decorators

add a dependecy library; add general decorator support
Merge pull request #2864 from butlermatt/master

Add FAQ about InvalidModificationError
update the authors file
Merge pull request #2895 from devoncarew/devoncarew_authors

update the authors file
merge master