Deleted the dthrust directory, placed the .hpp to hpx/components/vector and the .cpp to src/components/vector with the following changes:
1. Added the copyright
2. Modified the error.hpp for out_of_range exception
3. Modified the set_value so that it throws exception
4. Renamed the at API to get_value API
5. Added the default constructor to chunk_vector client class
6. Rename the <function name>_sync API to <function name> so that it confines to the standard library API