Fix bug in migration table builder.
updatet Testcase for Config Repository to show that Config::has fails on a true value because it weakly compares the values

updated Config Repository to strong compare the values which will lead to the correct result
Fix arraying of relations.
changed intends
Fix prefix issue on Memcached.
Merge pull request #2069 from Chumper/4.0

Config Repository fails on a true value due to weak comparison
Added contribution guidelines.
Merge branch '4.0'