Explicitly list .cabal files in cabal.project. Refs #622.

The `copilot-verifier` package was originally developed in an external repo
(https://github.com/Copilot-Language/copilot-verifier), but there is interest
in having all Copilot projects and libraries merged into the main
https://github.com/Copilot-Language/copilot repo for ease of management.

For now, we wish not to add `copilot-verifier` to the `cabal.project` file, as
its version bounds are tighter than the range of GHC versions that `copilot`
currently supports. As such, this commit explicitly lists the `.cabal` files of
packages that we do want to include in the `cabal.project`, i.e., all of the
`.cabal` files except for `copilot-verifier.cabal`.

Author: RyanGlScott

cabal.project

@@ -1,2 +1,10 @@
 packages:
-  */*.cabal
+  copilot-bluespec/copilot-bluespec.cabal
+  copilot-c99/copilot-c99.cabal
+  copilot-core/copilot-core.cabal
+  copilot-interpreter/copilot-interpreter.cabal
+  copilot-language/copilot-language.cabal
+  copilot-libraries/copilot-libraries.cabal
+  copilot-prettyprinter/copilot-prettyprinter.cabal
+  copilot-theorem/copilot-theorem.cabal
+  copilot/copilot.cabal