Switch tasks intents over to the new with syntax

The old syntax has been left in, but will display a warning when it is
used.
Update our tests to the new task intent syntax
Merge pull request #298 from Kyle-B/task-intent-syntax

This pull request adds support for the new task intent syntax to the compiler.
eg: `begin ref(x) foo(x);` --> `begin with (ref x) foo(x);`

All occurrences of the old syntax in the repository have been replaced.

The old syntax has been left in the compiler, but will display a warning when it is used.