Exceptions hierarchy

[ahmetb]

Currently all exceptions extend RuntimeException. We need a hierarchy for exceptions.

For instance:

• OrmanException (abstract ----+ OrmanSQLException (exceptions thrown while generating sql query builder org.orman.sql) ----+ OrmanMapperException (for mapper and mapping session exceptions from org.orman.mapper) ----+ OrmanQueryExecutionException (exceptions occur from external databases e.g. org.orman.[mysql|sqlite|sqlite.android])

some of them already under org.orman.datasource.exception. Move appropriate ones to org.orman.exception [new] package.