JetBrains license added.
Autoimport tests created.
.recommenders folder added to .gitignore.
Autoimport duplication fixed.

 #KT-5360 Fixed
Guava filter used for flitering autoimport proposals.
Most of methods are now static. New method for creating source files with specified packages.
Autoimport multitest added.
Performing multifile tests.
Multifile tests without parameters.