Improved documentation and cleaned up NamingHelper

1. Added documentation to toSQLNameDefault, toSQLName(Field) and
toSQLName(Class)
2. Rewrote toSQLNameDefault as implementation was hard to understand
(refactored to make it more readable)
3. Added additional test cases to NamingHelper and created helper method
assertToSqlNameEquals(String,String) this helps make the test case
more readable.

**Note:** I plan to add more documentation + tests where possible but before I do more work I want to know if this is something you guys actually want. By the way created an issue as I have not been able to properly configure Android Studio with Sugar, I have more or less set it up but as of right now I cannot run the tests.