Change API class names

Change all API class name prefixes from MMAPI to MAILAPI.

Add new config file which to hold constants such as:

* MAILAPI_ENDPOINT - holds the API url endpoint.
* MAILAPI_VERSION - holds the current version of the API wrapper.
* MAILAPI_PARTNER - holds the partner company name using the API. This value is mainly used for user agent.

Add license.php which holds license and file headers that are required by PEAR coding standards to be present at the top of each file and referenced it where appropriate.

Bumped up version to 1.0.3