CLOUDIFY-1532 Add logger facade class

- Add Logger class which is a facade on top of SLF4J's Logger.
- Add maven dependency for SLF4J-api
CLOUDIFY-1532 Add logger levels getters

- Add isDebug/Error/Info/Warn methods + tests
- Add maven dependency for testng, mockito and hamcrest.
CLOUDIFY-1532 Add logger levels getters

- Add debug overloads implementation + test