User-add random password support

I've used code from ipalib/plugins/host.py to add support for random
password generation. The '--random' option is now available in user-add
and user-mod commands. If both the 'password' and 'random' options are
used the 'random' option will be ignored.

Two test cases were added to unit test's module test_user_plugin.py -
they test creating and modifying user with random password. Two fuzzy tests
were added: test for password(string that doesn't start or end with
whitespace and doesn't containt other whitespace than ' ') and for whatever
string(because of krbextradata).

I've slightly modified ipa_generate_password in order to make passwords for
users more user-friendly(reduce number of non-letters). It has two optional
parameters now - first one is string of characters that should be used for
generating the passwd and second one is length of password. If none
parameter is set default values will be used so there's no need to modify
other plugins that use random password generator.

https://fedorahosted.org/freeipa/ticket/1979

tests/test_xmlrpc/xmlrpc_test.py

@@ -53,6 +53,16 @@ fuzzy_date = Fuzzy('^[a-zA-Z]{3} [a-zA-Z]{3} \d{2} \d{2}:\d{2}:\d{2} \d{4} UTC$'
 
 fuzzy_issuer = Fuzzy(type=basestring, test=lambda issuer: valid_issuer(issuer, api.env.realm))
 
+# Matches password - password consists of all printable characters without whitespaces
+# The only exception is space, but space cannot be at the beggingin or end of the pwd
+fuzzy_password = Fuzzy('^\S([\S ]*\S)*$')
+
+# Matches generalized time value. Time format is: %Y%m%d%H%M%SZ
+fuzzy_dergeneralizedtime = Fuzzy('^[0-9]{14}Z$')
+
+# match any string
+fuzzy_string = Fuzzy(type=basestring)
+
 try:
     if not api.Backend.xmlclient.isconnected():
         api.Backend.xmlclient.connect(fallback=False)