Support nested modules with namespaced plugin/proxy/log names

[loppear]

Resolves #127 and keeps all the hacks hidden away in NxusModule still?

Note that there are many different paths for determining the directory path prefix:

• When constructing a module instance that has been exported/required somewhere
  • uses require.cache so that static methods can also find this
• When constructing a module instance that is internal and never exported (happens in test, could happen elsewhere but probably doesn't today, but hard to ban)
  • uses old stacktrace-based approach since we are calling from constructor
• When calling getProxy in a module file before it is exported.
  • use the caller file under the assumption getProxy is only called next to module class definition
• When finding modules to import recursively in PluginManager
  • attempt to match _moduleName logic in effect for "Loading" message, but if using a module that has _moduleName this will be favored by the time the Application proxies etc.

[loppear]

Ok, so this is working correctly for application modules nested along with core modules. Core modules need the naming to come from the base module name (Router not nxus-router), ideally it would support better names for nested dep modules (nxus-router/src/modules/router-sessions -> router/router-sessions rather than current router-sessions)...