Ignore directory cache folder

Also ignore the apidocs folder (which is created on the current develop branch),
to make switching between branches easier.

Author: iMichka

.gitignore

@@ -4,6 +4,7 @@
 docs/_build
 unittests/temp
 unittests/data/pygccxml.cache
+unittests/data/directory_cache_test
 .idea
 dist
 build
@@ -12,3 +13,4 @@ pygccxml.egg-info
 .coverage*
 docs/examples/caching/example.hpp.xml
 test_cost.log
+docs/apidocs