Write the new docu section about caching;
second review of the caching section
Update auth_ldap.rst, adding caching section
Corrected typos
Merge pull request #1 from carlaschroder/auth_ldap

User Authentication with LDAP-- with cache section and fixes.
thx for remaster the caching section.
Merge pull request #549 from xtruthx/auth_ldap

New documentation section about caching;