Adjusting the C API to be more consistent with the original
Several cosmetic improvements to the API

- Enums are more consistent and concise (for the D API)
- Fixed a couple of callback names
- Improved example of simple client with D interface
Inserting copyright info in jack.d && simple_client_d_api.d
Removed unused imports in simple_client_d_api.d
Added new example: evmon_c_api.d
Added evmon_d_api example and extended the API wrapper implementation
Removed all the "Jack" prefixes from the D API