Update collectives

[everythingfunctional]

Updates the collective interfaces and implementations to match the new PRIF revision.

Some of the tests and implementations are currently commented out. This is because of the following compiler bugs:

• gcc crashes when trying to execute co_reduce
• flang does not support parameterized derived types yet
• flang does not support comparison operations on characters

Fixes #69
Fixes #132
Fixes #153
Fixes #154
Fixes #155

[rouson]

@everythingfunctional flang supports kind type parameters for derived types but not length type parameters. Does Caffeine use length type parameters?

[everythingfunctional]

Does Caffeine use length type parameters?

One of the tests was trying to demonstrate how co_reduce could be used with derived types with length type parameters. Otherwise Caffeine does not use length type parameters.