Implement configurable access modifiers for top-level types

[FriendlyChicken]

Top level types can have their access modifiers specified with --access or -ac, supports the following:

*=access
Name=access
Namespace.Name=access
Namespace.MethodsName.Name=access

Should be sufficient to close #186.

[ghost]

All CLA requirements met.

[tannergooding]

I missed that this had been opened and have also put up a PR to handle things: #279

The base approach between the two PRs are fairly similar, but #279 is addressing various perf considerations and has additional remapping functionality on top of what this one provides; as well as providing tests.

The notable differences are:

• using --with-access-specifier rather than --access (to match the other --with-* options that already exist)
• pre-parsing the specified remapping strings to AccessSpecifiers in the config constructor
• fixing a bug where protected and private access specifiers are invalid at certain scopes
• supporting qualified and remapped names
• using a cache to avoid additional name lookups showing up in the profiler
• test coverage

[FriendlyChicken]

Sounds good.