* Avoid clash between Backend.Dhall.Diagnostics.Range and Language.Haskell.LSP.Types.Range
* Ignore .cache dirs created by tests
* Fix rest of compile errors and warnings
prettyprinter doesn't match on lts-9.0. You get the following error
with stack:
```
Error: While constructing the build plan, the following exceptions were encountered:
In the dependencies for dhall-1.6.0:
prettyprinter-1.1 must match >=1.1.1 && <1.2 (latest applicable is 1.1.1)
needed since dhall-1.6.0 is a build target.
```
Javier Neira
Eric Conlon
Oliver Charles
Sibi