Create and populate user directories on useradd, delete them on userdel

Fixes: #212

* The resolv test case can now test for TXT and SRV resolving by
  specifying -t host and -s host respectively. The -n flag must still be
  passed in to enable network tests.
* Added test for the little complicated resolv_copy_hostent() function.
* Leak checking using the new tests common functions.
* Fix indentation for test_internet, since the whole function was
  modified to be able to handle SRV and TXT replies.
* Initialize the debug variable in main().

Also removed one unused variable in krb5_utils-tests.c

The leak_check_setup() and leak_check_teardown() functions can be added
to a test case with tcase_add_checked_fixture(). They will make sure
that all tests are checked for memory leaks. However, since talloc is
hierarchical and automatically frees the children, this will not catch
all cases, but might still be helpful.

The check_leaks(ctx, bytes) function takes a talloc context as an
argument and the number of bytes it should be using up (children
included). The total byte size used up by the context is determined by
the talloc_total_size() function. If the size doesn't agree,
check_leaks() will print out a talloc report on the context and makes
the current test fail.

The check_leaks_push() and check_leaks_pop() both take a talloc context
as an argument. Every time push is called, the context is "pushed" onto
an internal stack and it's current size is noted. When the context is
later "poped", the pop function will make sure that the size is the same
as when it was pushed. It will also check that it's not called
out-of-order or if the stack isn't empty.

- add a hint to the man page about permissions on sssd.conf
- add a test if a symbolic link can be opened

Use this new utility call to ensure that the config file is safe
to read from.

Implement a set of python bindings for the sysdb with feature set
similar to what is available in the tools. The primary
consumers would be applications like system-config-users.

Resolves: Ticket #102

The configuration options krb5ccache_dir and krb5ccname_template
are added to the Kerberos provider to create the user's credential
caches the same way as pam_krb5 does. Due to the design of the sssd
and the supported ccache types of MIT Kerberos only files are
allowed.