Use namespace::clean instead and have an explicit exclusion map

`namespace::autoclean` by default removes everything that doesn't look like a **method**, and as such the symbols injected by `MooseX::Types` get cleaned out, causing `06-fully-qualified.t` to fail
```
t/06-fully-qualified.t .. 
ok 1 - is_Path
ok 2 - type is available as an import
not ok 3 - type is available as a fully-qualified name
1..3

#   Failed test 'type is available as a fully-qualified name'
#   at t/06-fully-qualified.t line 14.
# Looks like you failed 1 test of 3.
Dubious, test returned 1 (wstat 256, 0x100)
Failed 1/3 subtests 

Test Summary Report
-------------------
t/06-fully-qualified.t (Wstat: 256 Tests: 3 Failed: 1)
  Failed test:  3
  Non-zero exit status: 1
```

So instead, use `namespace::clean` and have an explicit list of things not to remove.