Added trait_exists

Added trait_exists to the list of cases in Krautoload\Util::calledFromClassExists
Added trait_exists in a bunch of places
merge ClassFinder into ClassLoader
more default methods in abstract class finder api
InjectedAPI_ClassFinder_*: Reuse methods from Abstract, use @inheritdoc.
NamespaceVisitor is now NamespaceInspector
NamespaceVisitor is now NamespaceInspector
clean up searchable namespaces
NamespaceVisitor is now NamespaceInspector
Add a Mock for InjectedAPI_ClassFileVisitor_*.
composer.json: add keywords, change homepage, remove archive.
add fixtures for psr-x
PluggableClassLoaderTest only needs a ClassLoader, not a NamespaceVisitor.
Add a test for class discovery.
Add trait_exists() in addition to class_exists() and interface_exists() everywhere, but check function_exists('trait_exists') first. This does also merge in the pull request at https://github.com/donquixote/krautoload/pull/3 by paul-vg. The pull request had the OR pieces broken to multiple lines, which is reasonable.
Test PSR-X class loading.
Finish discovery and discovery tests.