Fix display of maps

[theunrepentantgeek]

Fixes the display of maps where the key or value of the map is a type declared in the package being documented.

The function typeDisplayName() is modified to be mildly recursive, applying naming rules to the key and value types before constructing the final display name.

Similar recursive changes are applied for slices and pointers, to ensure correct display even in edge cases - such as []*Foo where Foo is a type declared in the current package.

Closes #64